Why is Carracosta considered so mediocre/bad this gen? It has lost Z-Moves sure but is there more to it compared to how it was in last gen PU? Back there it also had to deal with things like Tangela, Qwilfish, and Poliwrath and came out just fine. Its been called to be unranked several times in the past and has been clinging to dear life in mid C/C- for quite a while.
I'm mainly talking about the Shell Smash set. I'm guessing the Rocker set has its own problems that the on-paper role compression in Scald + Rocks + Knock Off just can't really salvage.
The main reasons I think Carracosta is not very good is because of several reasons:
1. Power Creep
A lot of threats have fallen into PU, and by consequence, ZU. The multitude of fightings in PU has caused many threats, like Cinccino, Alolan Persian, and A-Dugtrio to also fall in. Several defensive answers like Tangela, Gurdurr, and Pyukumuku can stop a sweep before it even starts, and even when it eliminates a check, it can still be checked by the high amount of speed control in choice scarfers like manectric, sawk, and Gourgeist-S. Like you said, Poliwrath and Qwilfish still being common hurts its viability, as they can lessen its effectiveness through resistances and status. Grass types ranging from the versatile Tangela to the niche eldegoss are omnipresent as a result of Silvally-Ground’s dominance.
2. 4MSS
Of all the Pokemon with set syndromes, Carracosta has one of the worst cases (alongside maybe Hitmonchan) of 4-move set syndrome. It wants to run the obligatory Shell Smash + Stone Edge, which might seem okay at first… but then it wants Liquidation, Aqua Jet, Earthquake, and Superpower as well. Since it will usually struggle against Pokemon like Gurdurr and Tangela, it will also need to consider moves like Hydro Pump and Ice Beam just to deal with them...wait, Gurdurr isn’t even OHKO’ed by Hydro Pump? Unfortunate. This problem also extends to its ability, as it wants Sturdy to ensure it doesn’t get revenge killed (even though it is still hugely vulnerable to priority/fast attackers), but also Solid Rock to have a better chance against Silvally-Ground and Dugtrio (which still gets OHKOed by the plethora of grass types and Sawk). Heavy duty boots are needed to ensure sturdy isn’t broken, while white herb is needed to maintain its decent bulk.
3. Sluggishness
As
hiss pointed out, even at +2, Carracosta relies on maintaining an Adamant to deal with neutral threats like Perrserker and Silvally-Dark, as Jolly compromises even more power while still being slower than Scarf Sawk, Cinccino, and A-Persian. While its defensive typing allows it to neatly check Kanga and Ninetales in a pinch, its offensive capabilities offset the nice defensive stat + typing, such pokemon often carry coverage moves like EQ and Energy Ball to deter Carracosta. Assuming A persian is healthy enough, it can easily swat away a sweep by foul playing away thanks to fur coat. Mane and cinccino can stave off an Aqua jet if they’re at full health:
+2 252+ Atk Carracosta Aqua Jet vs. 0 HP / 0 Def Cinccino: 192-226 (65.9 - 77.6%) -- guaranteed 2HKO after Stealth Rock
+2 252+ Atk Carracosta Aqua Jet vs. 0 HP / 0 Def Manectric: 192-226 (68.3 - 80.4%) -- guaranteed 2HKO after Stealth Rock
As a side note, Crustle has been seeing more usage as a Shell Smash sweeper despite having a worse Bug/Rock typing and Rhydon gaining more stardom - its lack of a 4x weakness, crucial access to spikes, and better matchups against defoggers like Altaria and Articuno give it more incentive to being used, especially since it can also run a capable suicide lead set as such. Crustle’s higher speed allows it to actually outspeed Cinccino and Alolan Persian and actually beat them, since its STAB X-Scissor and slightly higher speed tier warrants more reliability on a game-to-game basis, even if its speed tier still leaves it to be outrun by scarf sawk and mane.
There is a lot of risk to put Carracosta in a team, and sometimes, it doesn’t offer a high reward when you compare to the plethora of other Water types and setup sweepers in the tier - it’s too slow, has too big of a set syndrome, and is just not happy with the increasing power creep.
Hope this hepls.