The surest way to appreciate the sheer flexibility of the wizard in Baldur's Gate 3 is to go play a mage in Baldur's Gate 1.
Go on. Hop to it. It'll be a life-changing experience, I assure you.
In any case, the real advantage to the wizard vs. the sorcerer, warlock, or bard is being able to learn spells from scrolls and just... have them in your spellbook at all times. The other wizard-adjacent spellcasting classes learn spells on level-up, which isn't too restrictive since you can respec with Withers, but it does mean that they lack the ability to freely swap prepared spells in and out without going back to camp and paying for a respec and going through the motions of DOING the respec level-by-level each time. So wizards can get a fair bit more use out of those situational spells, by virtue of not having as much pressure on them to choose between a situational spell at level-up and a more obviously flexible spell.
