I dont understand this thread.
Necromancers arent obliged to use only Necromancy spells, Illusionists arent obliged to use only Illusion spells, etc.
Literally the only advantage you get for spells of your type is that you can learn them cheaper from scrolls. Thats it.
Which ironically means if you want to learn all spells you better dont learn your own school at levelup, lolz.
So picking your School is really just a smaller part of being a Wizard, and really all about the extra features you get.
Like the Necromancer getting more and stronger Animate Dead summons etc, the Invoker or Evoker getting party friendly area damage spells for free and getting stronger Cantrips, etc.
Saying that any type of Wizard is trash is however absurd, because they all get the same spells. This is not like previous versions of D&D where specialist wizards would lose access to certain schools, to get an extra spell of their own specialization per spelllevel. Everyone is a specialist now, and everyone can cast all spells.
And yes Evoker get stronger Cantrips. Bo-ho. Damage dealing isnt the main task of any spellcaster, thats what we have fighters etc for.
In BG2 this was different. There we got Improved Alacrity, which turned especially sorcerers into the most brutal deliverers of spike damage. Of course right now Haste is still bugged in BG3, so you can actually cast two spells per round. And maybe Larian even likes it this way and it will thus stay this way.
Enchantment 10 is also very, very powerful of going single class Wizard for some reason. But yes, Illusion is garbage.
Divination is fantastic for a dip (and multi class wizards are the way to go in BG3 imho)
Evocation is great for a dip, also good if you go single class.
Abjuration and Enchantment are great for single class only
Transmutation is good for a camp wizard
Necromancy I’ve not tested enough to have an opinion
The rest are garbage
Since you just praised six schools, "the rest" is - Conjuration and Illusion.
