Wizards are more than fine in 5e, it's the Bg3 adaption of the ruleset is questionable. Concentration has already been mentioned and the controll spells being nerfed. Additionally BG3 is littered with OP melee weapons and gear which drastically changes the power balance between the classes. Add in no attunement and melee makes casters look like trash.
That being said, casters still add some tactical tools which can massively impact the battle. We are missing a critical gear type for casters though: spell foci. An Arcane Grimoire +2 increasing spell DC would be comparable to a +2 greatsword. We have a lot of weapons and gear for melee, very little that helps spell DC's. Casters seems to have been mostly forgotten in itemization that's useful and not just weird gimmicks.
