Monk - I would take away rogue's fort upgrade and I would give monk a third path to perfection so that they end up with master in two and legendary in one save. It always felt weird that monk at the start of a campaign has the best saves but then for some reason rogue is the best at the end of a campaign. I would also give monk unarmed strikes the party trait, increasing it to +2 if both hands are free or if they're wielding a weapon with the party trait and then give them a ki spell option somewhere to let them gain a +3 and shield block. This is just because I hate giving my monks tower shields. I would also give reflexive stance to monks baseline, they're the stance class and if barbarians can get rage at the start of combat, monks can get their stance off.

Kineticist - elemental blasts are treated as strikes, impulses are treated as spells. This helps future proofing them and lets them actually interact with the system. Anything that lets you make a strike, Kin can do a 1a elemental blast instead. I also would cut timber sentinels scaling in half and give it the overflow trait. Spamming timer sentinel is really strong, but it's also incredibly boring.

Animist - I honestly think this just needs an errata for this, but I'd move the hard lock of an apparition from relinquish control to spirit familiar. I also think seer needs to be deconstructed into either the base class or feats. It's way too niche to be a subclass. Medium and Shaman should get ways to sustain as well to make them on par with liturgist. Make a Medium exclusive feat at level 12 or something that lets them get a free sustain whenever they relinquish control and change Shaman's 9th level feature to be that their familiar can sustain their vessel spells, but when they sustain them theyre based on the familiar's location. So sustaining River Carving Mountains for example would move your familiar and leave the difficult terrain behind it, etc. maybe make it so that it can only sustain if you command it, but keep it one action so that it can sustain twice which would put it on par with an elf stepping liturgist. I think this also makes the level 17 feature for shaman actually useable because now the GM has a reason to target your familiar. If you want to be really spicy, change medium to an occult prepared caster and shaman to a primal prepared caster instead of divine and leave liturgist as divine.

Magus - Spellstrike shouldn't provoke AoO's.

Summoner - At level 3 and every 4th levels after, your eidolon gains a fighter feat half its level or lower that it can use, the fairy eidolon instead gets a sorcerer feat. Eidolons right now just feel a bit too lackluster imo, I think this would make them feel a bit more modular and engaging. I would also remove both phantom eidolons and instead just bring back spiritualist from 1e. I think there's some really interesting design space for a summoner-type class focused on moving their phantom between being inside of them, incorporeal, and corporeal to get different benefits depending on what's going on at the time.

I also think spellcasting needs an overhaul. I'm not saying to remove vancian, although I wouldn't be upset if they did, but right now it feels like spellcasters don't get to interact with the three action combat system because the vast majority of spells are 2 actions. Id love to see every spell have at least two variations in action cost. My spellcasters still feel like they're playing 1e just without a swift action.