I disagree entirely, that suggestion would make the game significantly less fun, albeit more like dnd 5e in some aspects, but overall I don’t think most people want 4 or 5 restrictions on the ability to get some spell slots. In fact I don’t really understand why even hardcore players would want that, the game by its self on normal when fighting 5 or more enemies is already a huge pain but the payoff is usually worth it and you can rest and recover after to at least have your melee fighters in tip top shape as it currently stands, but that change would neuter wizards as a whole for me personally as it would be no different than POE which i loved except for the fact wizards were 99% of the time worthless, and only cause further annoyance when they died after being useless (when they ran outta spells). I don’t want a repeat of that. Personally i want to see wizards in a better spot than right now as currently they are Imo the weakest of all the currently available classes, and no I don’t think that the individuality of warlock would be ruined as the main draw for me and probably some other people is the pet and evil eldritch feel of the spell warlock has that wizard can’t even get, the only class wizard can really copy somewhat is cleric but even then it is completely subpar because the wizard usually lacks wisdom to cast good cleric spells. This loss of identity for other classes from what i can tell would be non existent because the identity is based on what spells the spellcaster has and then the next defining factor would be how effective those spells are on said class. Also cantrips getting an extra die still would make them subpar on most classes as their damage (other than a few exceptions) is already low and the boost they get would barely bring them to lvl 2 eldritch blast territory. Also one of the only ways you can resurrect a party member is at the camp so multiple restrictions would hamper that as well.
Arguably, right now, Wizards are actually stronger than they should be if all you care is about damage/evocation (if it's concentration this game messes that up with surfaces a lot.) With how resting is currently constructed, a Wizard genuinely can use all their spells lots in a fight, every fight. This means they can spam all their non cantrip spells, when cantrips are supposed to be a wizard's basic attack. Also loss of identity is very major cause Wizard, Warlock, and eventually to be added Bard and Sorcerer (and maybe Artificer, a man can hope) have a large amount of overlap in their spell lists, so their class mechanics help greatly in making each unique. And being able to recharge spells lots so freely is the exclusive thing for Warlock.
Also, I quibble greatly with the idea that cantrips are useless, even in BG3. Cantrips are great if you know what you are doing with them, with no resource cost a caster can exploit elemental weaknesses, target what they think would be lower to hit, and inflict status like being unable to heal. Cantrips are the wizard's bread and butter since due to inscribing they can get so many of them (only Tome warlock in 5e being able to compete imo). Cantrips are the wizard's longsword, doing a similar amount of damage, but they have a variety of longsword that while not getting a stat bonus to damage can interact with combat in many different ways. And ooc, I actually love that larian removed the negative from friends making it no longer just an ok cantrip to a very useful one.
Because of cantrips, the only time Wizard is useless is if Silence is up or if they got hit too much, otherwise a good wizard always has a tool for the situation, even when out of resources.