A single 7th lvl spell is already too much, let alone a 9th lvl one. I'd say by the 5th spell circle you already have all the tools you'll ever need in a campaign, and you are already ridiculously powerful and more versatile than all martials, 6th circle is gravy on top and a reward for not multiclassing.
Wizards has worse hit dice, no weapon proficiency(...) You keep comparing then to marial, not trying to make martial better, but making casters worse..
"already have all the tools you'll ever need in a campaign"
In what campaign? You are thinking that fighting bandits on Faerun is every campaign and is not. Elemental planes, abyss, shadowfell, fey world, underdark(...) there are a lot of powerful enemies on that settings. Disagree? Pick NWN1, and try to defeat Vix'thra using only spells from tier 1 to 6. Note that NWN1 is 3.5e, which has way more powerful spells than 5e. If after 666 reloads, you managed to do that, try face mephistopheles on end of act 3 of hotu expansion with spells up to tier 6. Even on base campaign, try to face the final boss without using high tier magic. Try do that.
Try not use high tier magic in a game with far stronger magic than 5e.
I have the impression that "nerf A" crowd never played "A"...