the unlimited use, video game-like, powers that the players have. When you have casters who can throw around unlimited cantrips, that scale with level, with no depletion of slots or points or fatigue or anything, is total BS for anything even remotely "low magic".
I have to disagree with this last bit, a little. Whether magic is at will or daily makes little difference to blowing the 'low magic' vibe (though, of course, it all depends on what you mean by 'low magic,' too).
If magic can be used systematically, without risk or price, by anyone who learns how to do it, yeah, that blows low magic, whether you're systematically plinking away with an eldritch bolt every 6 seconds, or casting a wall of iron 1/day, every day, to undermine an economy.
OTOH, if the character tossing eldritch bolts is one in a million, can't do much more magic than that in combat and/or without risking severe consequences, and, if a PC, actually doing less damage with his eldritch bolts than the same-level PC archer is with his arrows, that's not so bad. The setting is still 'low magic' and, on the PC side, the magic isn't overpowered or overversatile or prone to the kinds of systematic (ab)use that can shatter the sense of that magic being rare and limited.
Something that irks me when people refer to 5E as "low magic" is that it is really only low magic in the expectations of how many permanent magic items your character needs is his career to survive fights with tougher and tougher enemies. It is in no way "low magic" when it comes to the magical abilities of most of the character classes and sub-classes. That is what I would want to see reined in and what my past post in this thread was directed at.
There are potentially a lot of ways to do that. D&D casters have, historically, not had as much, as easy, or as safe magic as in 5e. It'd be simple to re-instate some of the limitations on casting, including spell interruption and slot loss, for instance. Imagine if spells all had a full-round casting time. You start casting with your action, on the start of your next turn, the spell goes off. You could still cast 1 spell/round, it's just if you get hit while you're casting *poof* (or, make a concentration check, I suppose, if we want easy mode).
