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.[/spoiler]
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.
Fighters also get Action Surge and either spells if you choose Eldritch Knight or Superiority Dice if you choose Battlemaster.
You should try these features out. They truly affect combat. A Battlemaster's abilities recharge on a short rest and an Eldritch Knight's spells recharge on a long rest.
I'm glad for you if "you know DnD better than I" but resting is not at all what makes the game's difficulty. It's only a small part of it and the player can choose to rest often or less often. The player can choose to have something a bit more easy or not.
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 and so on).
And how easy a battle is depends quite a bit on how many resources you have to take down an enemies hit points to zero.
If your party has full resources they can even take enemies down before they get to use their features and abilities.
They could definitely let us choose how much we want to be restricted by food supply / ressources management or not.
Impose to those that want fireworks at every combats to play unchallenging combats is a really stupid idea because resting is NOT what makes combats challenging or not.
I'm certain you will get to choose how easy you want combat to be, in most computer games that is tied to difficulty level.
