Hilariously, getting rid of short rests in favor of long rests (the suspected plan for 5.5) does absolutely nothing to resolve this lol.
I've actually started to dabble in homebrew to do the opposite for my own games. Pulling back full caster spells and setting everyone to either 'per encounter or 'at will.'
Currently for full casters it's 2 cantrip slots (ala 3E, but stronger and with some scaling) and 1 spell slot gained of the highest level they can cast gained at each character level. So 1: 0/0/1 | 2: 0/0/1/1 | 3: 0/0/1/1/2 etc
Only playtested it a little, but so far it's working well.
EDIT: To clarify, spellcasters don't instantly regain their spells but I don't have a short rest mechanic sorted out either. Since nobody's asked to play a spontaneous caster yet, I've just been rolling with 1 minute to prepare a spell + 1 minute per level of the spell. (0=1, 1 =2 etc)
Well, if they make it so (frex) Battle Masters can recharge their Superiority Dice with a five-minute exercise PB times per day, then it will close some of the gap. Not all of it by any means, but some, and "fix
some of the problem but not all of it" is kind of 5e's manifesto. Concentration fixes
some of the problem of magic being OP, but not all of it. Reduced spell slots (relative to 3e) and no automatic scaling reduces
some of the "linear fighter, quadratic wizard" problems, but not all of them. Feats/ASIs being tied to class level, plus ability score prerequisites, fixes
some of the problems with
a la carté multiclassing, but not all of them.
(This doesn't touch on the new problems 5e created, of course, like the "you fall behind on 4 of 6 saving throws so attacks based on saves are too powerful" problem, or the Ghoul Surprise, or the lack of design purpose behind most subclasses leading to many of them being super weak, e.g. Champion, Berserker, Beast Master, Four Elements, etc., and a few being excessively strong, e.g. Twilight, Moon at certain levels, Hexblade, etc.)