Oh, please. You're saying that meteor swarm is only worth it if it's cost-effective against one target with Legendary Resistance? It has an AoE of eight hundred squares and averages 140 damage! It's a spell for taking out hordes of tough foes. You can kill or cripple two dozen frost giants with one spell (they need a natural 20 to make the save)--and if you think frost giants are "yips," I suggest you try taking on 24 of them with a 20th-level fighter and see how far you get.I think the one thing that bothers me about *any* conversation dealing with caster nerfing is the assumption that every player is trying to "steal the spot light" and "end the encounter in one round." Frankly, it's rather irksome that every time I bring up an aspect of the new casting system I dislike, it's assumed I'm upset because I don't get to be the most powerful character anymore.
My issue is I think the nerfing went too far; there's no point of using your big spells when they would be most useful, because every big bad scary thing that needs its teeth pushed in with a meteor swarm gets to auto save on top of having some kind cheap resistance to magic or weird lair benefits. So what's the point of even having a meteor swarm when it won't ever be used to its full potential? And I don't claim to know much about "bounded accuracy" or whatever it's called, but the idea of blowing a 9th level spell on a bunch of yips- because let's face it, they're the only ones who will actually be effected- leaves a sour taste in my mouth.
As for "needing" to blow higher-level slots to keep direct-damage spells effective: No, you don't. I'm playing a 13th-level wizard and I mostly throw straight-up, level 3 fireballs. They work just fine. 8d6 is a good solid hit at this level, enough to kill weak foes and rock stronger ones back on their heels. When dealing with a single big foe, I provide support for the barbarian and the monk, using dimension door to get them where they need to be, providing distractions, and counterspelling enemy magic. When there's a lot of enemies, the barbarian and the monk play bodyguard while I lay waste. They have their specialties and I have mine.