I think you're actually onto something legit here - the vanilla Conjuration tree really does incentivize the "summon and forget" playstyle, especially once you hit Dremora Lords. But there are ways to make it feel less like you're just pressing a button.
First, stop thinking of summons as tanks. They're better as force multipliers - use them to lock down one target while you're actually casting something else. Like, summon a Dremora Lord to tie up the big enemy, then you're free to cast Mayhem or just fling destruction spells at the rest. The summon doesn't have to solo the dungeon. You do the actual work.
Second, there's a perk in the Conjuration tree - the one that lets you summon two creatures at once - and honestly that's where it gets more interesting. Two weaker summons (like Atronachs) are way more engaging to position than one meat shield. They die faster, so you're actually thinking about placement instead of just... existing while they fight.
Third, the Necromage perk is stupid good and people sleep on it. Raise a corpse, cast a Dremora summon, and suddenly you've got a small army that's actually yours instead of just demons you borrowed. Feels more like commanding forces than babysitting.
Magicka costs are real though. If you're running out, you're probably not investing enough in Magicka itself or you're casting too many summons at once. The Atronach stone helps, or just... don't maintain three summons. One, maybe two. Cast something else with your magicka.
What difficulty mods are you running, if any? That changes the math a lot.