I think some of the arguments made in favor of tera are very misleading and may have even been made in bad faith, so I'd like to go over some of them.
1) Set up sweepers are dangerous with or without tera
Technically true, but they're much, much stronger with tera. Usually, a set up sweeper buys one turn of set up by forcing a switch. But with tera you get that, plus a free turn using tera to tank a move that would normally one shot you, plus another free turn as your opponent is forced to switch again. "Just don't let x sweeper set up" is a poor argument, because you can't know what you're trying to stop until you force the tera, which will inevitably give your opponent free turns to continue boosting. By the time your actual counter comes in, it's probably too late.
No you can't. Roaring moon can be flying, ground, dark, or steel. Dragapult can be ghost, dark, dragon, or fighting. There's nothing you can do to cover all these options. There's no way you can tell which it is. Most mons have at least 2 or 3 common tera types plus 1 or 2 less common (but still viable) sets. They all run simlar moves, stat spreads and items too, so there's no way to deduce what they're running or narrow things down. All you can do is guess blindly.
3) Tera will get more predictable when the meta stabilizes
It probably won't. Remember early on when roaring moon was always tera dark? Then people started to rely heavily on bulky fighting and fairy types, so they switched to flying and steel. Then people used bulky steels instead, so tera ground became more popular. Once patterns and trends emerge, people look for ways to counter or take advantage of them. Evidence suggests tera will only become more unpredictable over time, especially when home drops.
4) 50/50s are normal for pokemon
True 50/50s are rare, and should stay that way. Besides, Tera is worse than any 50/50. To predict tera you know exactly when and how it will be used. You can't send in a fighting type on dragonite before they decide to tera, which leads back to my first point. You can try double switch to bait and predict, but then you're just giving your opponent 2 free turns instead of three. And if you're wrong, you also end up sacking a mon for no reason. The risk/reward is heavily in the dragonite's favor, and they don't even have to use tera to reap the benefits. It's not a 50/50, it's a 1/3 at best. For mons like roaring moon, it's a 1/5.
5) It's just a one turn surprise
Tera matters more than just on the turn it's used. Every turn someone can tera, you have to consider it. Tera forces guesses worse than a 50/50 every turn there's even a slight chance your opponent could use it. This is already hurting the tier. I've seen chien-pao click crunch on my ting-lu when I have no ice switch-ins only to get body pressed. I shouldn't win interactions like that. I'm not looking forward to a meta where people are randomly throwing out not very effective moves in the hopes of catching a tera.
6) Tera is just like megas, z-moves, items, or lure sets
Tera has no opportunity cost, has no tell, requires no commitment or sacrifice in the builder, and rarely has any risk or downsides. (Gaining weaknesses doesn't matter if you choose when you have them.) Despite this, it can completely change any pokemon's counters, grants huge damage boosts, and is extremely unpredictable. Megas take your item slot and are very predictable. Z-moves take your item slot, are a one time nuke with no defensive utility, and are still much more predictable than tera. Other items can be knocked, tricked, scouted, and have severe downsides in the case of choice items or life orb. Lure sets sacrifice a ton to prey on their usual counters, (Perish song azu for example, isn't exactly a great sweeper) You can make a point by comparing two different things, but you have to admit that tera is much closer to dynamax than any other gimmick. The stab boost alone is like a z-move every turn. If tera were an item, it would be every pokemon's best choice.
7) We can just ban the worst abusers
Very few of the "abusers" do anything unique with tera. They're just the pokemon with the highest stats. If roaring moon were banned people would just switch to dragapult or salamance or gyarados. Chi-yu, annihilape, roaring moon and dragonite would be more bans than z-moves ever caused, and home will bring koko, lele, regieleki, regidrago, blaziken, etc. If half of OU needs to be banned because of tera, then it's the mechanic that needs to go.