You are asserting that spellcasters being able to use every spell in every combat only changes the difficulty a bit -- that's funny.
It's possible you aren't familiar with D&D and don't know how to use the character's abilities to full effect, which seems to be the case from your comment.
If that's the case I suggest you try to play a few playthroughs just using your character's abilities and you'll see how powerful they are and how having access to them every battle trivializes combat
Once again, it looks like your "roleplaying" self contraints doesn't give you a clear vision of how the game really works.
Of course it's a bit easier with all your spellslot if you play a caster... But the game is not way more easier with spellcaster and long rest based classes than it is with other classes.
In exemple fighters don't need to rest at all (eating pig heads is better than second wind), and every classes can use the tons of scrolls like if they were wizards.
I'm glad for you if "you know DnD better than I" but resting is not at all what define the game's difficulty. It's only a small part of it, a tool the player can choose to use often or less often.
Food supply will only define if you can rest more or less, nothing related to the core difficulty elements (ennemy's AC, HP, ennemy's features, abilities, numbers of ennemy's, resistance,... and so on).
They could definitely let us choose how much we want to be restricted by food supply / ressources management or not.
But impose to those that want fireworks at every combats to play unchallenging combats is a stupid idea because the resting mechanics alone does not at all determine the difficulty of the game.
It's only a small part of the picture.
