I think to figure out the reason that some people are calling for the Slow twins to be looked at you have to examine this gen's meta at large which I'll discuss in a few points:
1. Lower power level+Heavy-Duty Boots:
Heavy-Duty Boots was by far the largest buff defensive pokemon could receive. Hazard chip is so essential to breaking fat teams that last gen stall teams dedicated a full third of their squad(M-Sableye+Defogger) to stop hazards from going up despite pretty much every member of that team being neutral or resistant to them. HDB also allowed mons to become walls that would have been average at that role(Zapdos) or even unviable altogether(Moltres) due to their 2x and 4x Rocks weakness, respectively. Zapdos coming in at 75% meant that the things it was supposed to check were suddenly in a much more propitious position to break through it. Furthermore, these aforementioned walls also love the fact that Z-Moves and Megas are gone. The removal of Z-Moves also means that you can tell if certain offensive mons on your team are going to be deadweight in your matchup, IE even though Volcarona loved the addition of HDB, its currently quite mediocre in OU due to the removal of HP Ground and Psychium Z. Lure sets are all but gone, meaning that you will make pretty much no progress if your opponents check to your offensive mon is kept healthy, which is easier than ever considering the hazard immunity HDB grants. No longer does Zapdos, one of the best Kartana checks, have to fear a +2 Normalium Z blowing it away.
2. Lack of punishment to passive play
The main reason WishPort Clefable was considered so irritating in the earlier stages of the meta was the lack of mons that could force its team into a bad position by it coming in. Clefable switching into a U-Turn from a mon it could theoretically check like Pheromosa used to be open territory for dangerous breakers you dont want to let in for free like SD Mega Scizor, Mega Mawile,or Icium Z Kyurem Black. Similarly,Slowbro last gen invited in Ash-Greninja and also forced you to run a Dark resist that wasnt a water type to avoid stacking weaknesses. Since most special attackers are sub-OU because of Teleport Blissey, Slowbro has much less to worry about this gen than last. The real only physical attacker that can force Slowbro out with the threat of an OHKO is Urshifu, meaning it can pivot in on the vast majority of offensive pokemon(including Pheromosa, as even banded U-Turn is nowhere near close to an OHKO from full). This essentially means that Slowbro is able to fire off risk-free Future Sights all game with little to no opportunity cost. This grants breakers the chip needed to bust through the walls they otherwise couldn't due to everything being immune to hazards. While I don't think this is necessarily a healthy mechanic, it's no more unhealthy than Toxapex being able to stay in on a strong super effective hit like LO Excadrill's EQ, Knocking off its item or attempting to scald burn it, and then switching out to regain the vast majority of the HP it just lost. The only reason that Future Sight Bro is seen as alarming is that it enables offensive mons instead of defensive ones, which brings me to my next point.
3. The winners of the recent bans
With Landorus, Zygarde and Kyurem-B gone(I think Landorus definitely was deserved, Zygarde was a maybe and Kyurem-B should have at least got a suspect test as it only shone against fat teams that it could sub in front of) several defensive mons won:
Pex was victimized by all 3 of the bans for obvious reasons. Even max SpDef couldn't save it from getting OHKO'd from Lando's Earth Power, meaning that Lando got a free Gravity as it switched out to its Flying type teammate. Kyurem used it as setup fodder, and Pex wouldn't dare try to Haze away its boosts for fear of eating a +1 Fusion Bolt. Letting Kyurem get behind a sub for free is especially bad because of Teravolt ignoring abilities like Unaware, meaning that even switching to Bold Clef meant that you were taking a huge chunk of damage. The presence of Kyurem alone in the tier meant that Toxapex was not as splashable as it was pre-DLC, not to say anything about Landorus-I, which pushed its usage down by quite a bit.
This is another mon that loved to see all 3 gone. Lando and Zygarde were two Ground types that it couldn't counter for obvious reasons, and it disliked eating boosted Fusion Bolts from Kyurem as well.
Clefable especially enjoyed the banning of Landorus-I, as its middling bulk really started to show when faced with boosted Sludge Waves and Earth Powers. If running Bold it had a good chance of being OHKOd from full, and if running Calm, it became much more vulnerable to Urshifu later in the game. Unaware Clef was a solid counter to Zygarde, but it was easily worn down from Toxic which Zygarde sometimes carried for Slowbro and Tangrowth. Kyurem-B also threatened the OHKO on even Unaware Clef due to Teravolt and its massive attack stat.
As you can see, the mons that benefitted most from the bans were slow, passive mons. While I don't think Future Sight Bro is the best thing for the meta, chip damage is part of the game and prevents games from going 100+ turns so I think that for the time being it should stay.
1. Lower power level+Heavy-Duty Boots:
Heavy-Duty Boots was by far the largest buff defensive pokemon could receive. Hazard chip is so essential to breaking fat teams that last gen stall teams dedicated a full third of their squad(M-Sableye+Defogger) to stop hazards from going up despite pretty much every member of that team being neutral or resistant to them. HDB also allowed mons to become walls that would have been average at that role(Zapdos) or even unviable altogether(Moltres) due to their 2x and 4x Rocks weakness, respectively. Zapdos coming in at 75% meant that the things it was supposed to check were suddenly in a much more propitious position to break through it. Furthermore, these aforementioned walls also love the fact that Z-Moves and Megas are gone. The removal of Z-Moves also means that you can tell if certain offensive mons on your team are going to be deadweight in your matchup, IE even though Volcarona loved the addition of HDB, its currently quite mediocre in OU due to the removal of HP Ground and Psychium Z. Lure sets are all but gone, meaning that you will make pretty much no progress if your opponents check to your offensive mon is kept healthy, which is easier than ever considering the hazard immunity HDB grants. No longer does Zapdos, one of the best Kartana checks, have to fear a +2 Normalium Z blowing it away.
2. Lack of punishment to passive play
The main reason WishPort Clefable was considered so irritating in the earlier stages of the meta was the lack of mons that could force its team into a bad position by it coming in. Clefable switching into a U-Turn from a mon it could theoretically check like Pheromosa used to be open territory for dangerous breakers you dont want to let in for free like SD Mega Scizor, Mega Mawile,or Icium Z Kyurem Black. Similarly,Slowbro last gen invited in Ash-Greninja and also forced you to run a Dark resist that wasnt a water type to avoid stacking weaknesses. Since most special attackers are sub-OU because of Teleport Blissey, Slowbro has much less to worry about this gen than last. The real only physical attacker that can force Slowbro out with the threat of an OHKO is Urshifu, meaning it can pivot in on the vast majority of offensive pokemon(including Pheromosa, as even banded U-Turn is nowhere near close to an OHKO from full). This essentially means that Slowbro is able to fire off risk-free Future Sights all game with little to no opportunity cost. This grants breakers the chip needed to bust through the walls they otherwise couldn't due to everything being immune to hazards. While I don't think this is necessarily a healthy mechanic, it's no more unhealthy than Toxapex being able to stay in on a strong super effective hit like LO Excadrill's EQ, Knocking off its item or attempting to scald burn it, and then switching out to regain the vast majority of the HP it just lost. The only reason that Future Sight Bro is seen as alarming is that it enables offensive mons instead of defensive ones, which brings me to my next point.
3. The winners of the recent bans
With Landorus, Zygarde and Kyurem-B gone(I think Landorus definitely was deserved, Zygarde was a maybe and Kyurem-B should have at least got a suspect test as it only shone against fat teams that it could sub in front of) several defensive mons won:
Pex was victimized by all 3 of the bans for obvious reasons. Even max SpDef couldn't save it from getting OHKO'd from Lando's Earth Power, meaning that Lando got a free Gravity as it switched out to its Flying type teammate. Kyurem used it as setup fodder, and Pex wouldn't dare try to Haze away its boosts for fear of eating a +1 Fusion Bolt. Letting Kyurem get behind a sub for free is especially bad because of Teravolt ignoring abilities like Unaware, meaning that even switching to Bold Clef meant that you were taking a huge chunk of damage. The presence of Kyurem alone in the tier meant that Toxapex was not as splashable as it was pre-DLC, not to say anything about Landorus-I, which pushed its usage down by quite a bit.
This is another mon that loved to see all 3 gone. Lando and Zygarde were two Ground types that it couldn't counter for obvious reasons, and it disliked eating boosted Fusion Bolts from Kyurem as well.
Clefable especially enjoyed the banning of Landorus-I, as its middling bulk really started to show when faced with boosted Sludge Waves and Earth Powers. If running Bold it had a good chance of being OHKOd from full, and if running Calm, it became much more vulnerable to Urshifu later in the game. Unaware Clef was a solid counter to Zygarde, but it was easily worn down from Toxic which Zygarde sometimes carried for Slowbro and Tangrowth. Kyurem-B also threatened the OHKO on even Unaware Clef due to Teravolt and its massive attack stat.
As you can see, the mons that benefitted most from the bans were slow, passive mons. While I don't think Future Sight Bro is the best thing for the meta, chip damage is part of the game and prevents games from going 100+ turns so I think that for the time being it should stay.
Magnemite. I mean seriously look what this thing has that people hate.
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