1 year since I switched from 5e to Pf2, and I gotta say that casters actually feel stronger in Pf2 than 5e.

Concentration is gone

5e had a mechanic where most spells with a duration required concentration (unrelated to the concentration trait in Pf2) and you could only concentrate on one spell at a time. Many things could cause you to break concentration and end the spell (e.g. damage forces a save, conditions like incapacitation auto-break concentration). In Pf2 this doesn't exist; you can stack Bless, Invisibility, Haste, Slow, etc. have multiple buffs/debuffs ongoing. The closest thing is spells that require sustain, and you could max out your action economy and have 2 sustained spells at once (even more if with options like Cackle and Effortless Concentration).

No arbitrary house rules that "fix" 5e casting

RAW 5e spellcasting is more powerful than Pf2, but in most games the DM tries to fix this by banning problematic spells, nerfing them, or adding teleportation on all boss monsters once you learn Forcecage. This leads to casters feeling artificially weaker compared to Pf2. 5e has a lot more imbalance which leads to the DM often adding a layer of homebrew rules to balance things, sometimes too much in the other direction.

Control spells still do something on a success

In 5e, the most powerful spells took enemies out of the game on a failed save and nothing on a success. In Pf2, the most difficult enemies will probably at least succeed. Spells like Roaring Applause, Slow, and Synesthesia still have a debilitating effect on a save, so rarely are your turns completely wasted.

5e enemies can choose to auto succeed and be unaffected by most spells that require a saving throw using Legendary Resistance (mid-high level bosses), whereas in Pf2 there's no auto-crit succeed ability.

Knowing good spells from bad is still important

Pf2 still has a crapload of garbage spells just like 5e. Knowing which spells are powerful and versatile makes you a better caster.

My experience in Abomination Vaults as a resentment witch

I played a resentment witch in AV and went with an extreme minmax approach. Notable spells I always prepared:

• Laughing Fit/Roaring Applause: MAPless strikes are strong, taking out an enemy's reactive strike halves how often they get a MAPless strike per round.
• Slow: taking out 1/3 of an enemy's action is extremely strong, often single handedly won boss fights because it allowed the party to kite in combination with tripping and door slamming.
• Max rank Calm: incapacitates mobs and renders most of them harmless until you kill the other half that succeeded.
• Synesthesia: cripples boss fights by nerfing their AC, speed, offense, and spellcasting.
• In combination with my witch abilities, I was often sustaining Laughing Fit, extending Slow with familiar of ongoing misery, and repositioning myself so enemies either gave up being able to hit me or had to eat multiple reactive strikes to try.