To support non-caster parties, however, the game has to massively chance it's model where certain problems can only be dealt with magically. From spell design to monster design, there are always scenarios where not having magic makes a scenario massively more difficult to impossible.
The classic fix has always been more common magic items, but with them being optional and artificially limited by attunement and rarity, the default game doesn't make this viable. Thus the DM has to step in and avoid using certain challenges and offering alternate solutions beyond "player casts spell".
I mean, ask yourself this. Is a campaign where no one plays a Fighter more or less difficult than one where no one plays a Wizard? Is a campaign where no one plays a Rogue more or less difficult than one where no one plays a Cleric? Is a campaign where no one plays a Barbarian more or less difficult than one where no one plays a Bard? Is a campaign where no one plays a Monk more or less difficult than one where no one plays a Druid?
Ideally, it shouldn't matter. But it does. And even if all of these classes I just mentioned were somehow banned from the game, you'd still have Rangers, Paladins, Artificers, Warlocks, and Sorcerers!