way more subjective than it might appear.
True, and that is unfortunately the biggest issue with it.
5e is by far the most "balanced" edition of the game, for as much as it's even possible
I always found 1E to be more balanced. But again, it is subjective--as you say.
All things that made casting super tedious except maybe casting times.
Tedious to you (and probably others, I'm sure!), but not for me (or others as well, I know), but they did help balance things.
Per slot spell prep in particular isn't on fire enough.
But is a HUGE balancing point, regardless.
It’s usually a discussion that boils down to the following:
“Wizard spells give them large amounts of direct influence in all three game pillars, fighters only have the combat pillar and they don’t excel at that enough to justify only being competent in it alone”
“Well fighters have their skills and feats and backgrounds right? They can use those for leverage in the other game pillars”
“Except wizards have access to skills, feats and backgrounds too, but with spells on top of those that are often auto-successes bypassing the need to roll at all, and the fighter’s feats are often required to be consumed on combat oriented feats to keep pace on DPR”
Sure, that is a typical back-and-forth. I know (for myself) I argued the bonus feats fighters get could be used of those other pillars, as they other feats can help with keep pace on DPR (something I've never concerned myself with in any serious fashion).
However, I also recognized that wasn't really enough to match what spellcasters (again, not just wizards) could do. So, balancing spellcasters (which can be done in a number of ways--my preference) or increasing martials (not so much my preference, although I think they need a bump anyway... just not as much as some others want) is the way to go, or a point of both in between.