Why would spellcasters be sitting on the sidelines? Yes, they're going to be casting cantrips on a regular basis, but that's what cantrips are for. Casters don't need to be spamming leveled spells every round in order to contribute.Yes, I've tried it and thought it was terrible for my playstyle.
The "balance" was that casters would sit on the sidelines with literally nothing to do. Meanwhile, every monster or enemy could "go nova" every encounter because - well, they're not going to survive to get a week-long rest anyway.
And if I'm going to play a game like that, I'll play an OSR system where the one spell you get a day actually matters. Not like a "hold person" that lasts for one round.
In any case, you do you. I and my group have a lot of fun and several of them are DMs who have commented that for the games that they run they've switched to the gritty rest rules because it works. Resource management should be part of running a caster.