I think the 4e/5e changes to magic and the way spellcasters were presented really sucks. They basically aimed to make wizards and other spellcasters as standard ranged characters with a "reskinning" of magic. End result is magic really doesn't feel magical anymore.
Sure, 4e committed the unpardonable sin of balancing magical and non-magical classes, so if the only way for something to feel magical is strict superiority, you could have complained about it then. But, I find it hard to believe that 5e magic doesn't feel magical on those grounds. Martial characters are back to just rolling to hit and rolling damage, spells are back to forcing saves and arbitrarily doing just about anything. Sure, some cantrips just attack AC and just do damage, but others require saves, have other effects, and most do damage types not readily achievable in a mundane way (ie other than slashing, piercing, bludgeoning & fire).
Casters in books or movies have better things to do than abuse generous spell systems. This is not a book or movie, this is a rpg. Moreover, it is D&D. Not exactly the kind of freeform storytelling system where you can trust players to self-regulate. No, if D&D allows a player to cast 14400 Firebolts a day, that's what he'll do if it gets him out of jail risk free. Or dispose of bodies. Or do this. Or do that.
Firebolts burn things, bottom line. So does mundane fire. Time not being an issue, you could burn something without magic, too. I suppose you could acid or radiant things to an annoying degree with cantrips, though.
Sure, systematically casting magic in an RPG makes it feel less magical (far more so than balancing magic does), but 1/round or 4/day is different only in degree, and not even that different. And, sure D&D magic suffers from that (systematic casting, not balance, that is), always has - still will even if you start cantrips at 4/day like it really was AD&D all over again.
Requiring a focus to cast spells is problematic. There's a reason we don't do that - it would be akin to being able to throw away the big guy's sword and now he can't fight, like, at all.
Well the big guy doesn't fight as well without it, but he can still punch you, he can pick up some improvised or less-favored weapon and do a little better than punching you but not as good as with the sword. The wizard without a focus, even if you made all cantrips require a focus, could still punch you, too, whether you want improvised foci is up to you.
Re: the slots aren't finite argument - sorry, but I don't have to fix the world's complete logic. Only enough so it works in the player characters' "bubble". Meaning I'm not so concerned about rational economics so much
Maybe shouldn't have used economic impact as an example, then. But, slots aren't finite, they're a renewable resource. Sure, they don't grow on trees - trees take a whole season to bear a new crop, slots renew every day!
as I'm irked by how trivially the game can say "you know all those fantasy movies lately, hobbits and khaleesis and all, and how their world feel... used, lived-in, believable? Well, forget all about that because in this game the wiz has an unlimited ability to make everything and everybody look squeaky clean with not a teared shirt or broken wagon wheel.
Why do people look grizzled after a long journey? Is it because they can't spruce themselves up without magic? No, it's because they get tired and /don't/. You don't need to change rules to get that affect in spite of the odd mending or prestidigitation cantrip, you just need to make rulings. Rule that a cantrip from an exhausted caster doesn't have quite that same cosmetic effect anymore, for instance.