spells that you would never want.

[Zanos]

Most damage spells are highly situational. If we take fireball as the baseline, the average CR 10 threat has 130 HP and a reflex save of 8. So our hypothetical level 10 wizard with lets say 24 intelligence has a DC 20 fireball, meaning that the enemy fails on an 11 or lower. So the fireball does on average 35 damage, and 45% of the time the damage is halved. Net average of 27 damage. That's five or so casts to drop him, without factoring in elemental resists or spell resistance. Doesn't look great. But fireball is an area of effect spell, meaning that it is incredibly inefficient on single targets. If we instead have an encounter of 2 CR 8 threats, which is the same total CR, the saving throws and hit points both go down, so the average number of casts to finish the encounter goes down to 3.3. If you take an encounter of four CR 6 threats, the number of casts required drops to 2.4. Keep in mind that these aren't your highest level slots, since at level 10 you have 5th level spells and could empower a fireball and that makes the average damage shoot up significantly. Back to the single target guy, you can maximize a scorching ray, and with a +1 bonus to caster level could easily be hitting his touch AC with maximized scorching ray for 72 damage, give or take 5% from critical hits and misses, and you're back to finishing the entire encounter in two casts.

This is a simplistic analysis against a foe with no SR or elemental resistance, but keep in mind these encounters should be fought with 3 other party members. I think a white room analysis that has a wizard able to solo kill many threats in 2-3 casts with direct damage with relatively minimal investment is pretty good. It's not like maximize or empower are really niche feats. Are there better options? Sure. Is damage particularly bad if your DM constantly hits you with single threats, or encounters that are substantially above your ECL? Yeah. If you don't have a way to bypass or overcome elemental resistance or SR, is it going to dig into these numbers? Absolutely. But I don't think you can say doing direct damage with spells is bad unless you're applying your damage spells unintelligently.