Thank you Tetra.
Avernus may suffer from the same problem as Frostmaiden - it was written with the assumption that magic items would also be handed out according to AL rules, and so they forgot to add in a sufficient quantity of items.
My observations as both a player (wizard, 6th level) and a DM (3rd to 13th level, high-magic item):
Primary casters
Clerics are fine with or without magic items, although this may differ a bit for a melee cleric.
Druids are likely the same, varying by school, with moon druids being less dependent.
Wizards do fine either way - my abjurer has nothing attuned. My resources have gone towards more spell scrolls. Denying wizards spell scrolls hurts. Mind you, I wouldn't turn down Bracers of Defense or a Ring of Protection or something. A wand might be nice.
Sorcerers - same, except they have fewer spells than wizards, so they could benefit more from the versatility added by a magic item.
Bards - I have never seen a bard in play. They're probably a mix.
Attack-roll types
Paladins, monks, fighters, rangers, rogues, and barbarians all benefit from magic weapons help them get the chance to land their smites and active abilities. They are typically the first targets for enemy attacks and for many AOE spells, being in front, and so benefit more often from defensive items than back-line casters. Wondrous items that add mobility and other options are helpful for adding uniqueness to their gameplay. You can build three wizards with the same subclass into different playstyles just by choosing different spells, but aside from Battlemaster, the front-line classes don't have that much versatility within a single subclass.
Being "the guy who has the spider armor and spends half his time attacking from the ceiling" or "the one who surrounds himself in a Fire Shield from his armor before diving into the middle of the enemy formation" or becomes a lot more character-defining.
Artificer
At high levels, they make their own items given enough time. An artificer without magic items is under-powered.
The martial/caster item dependence disparity isn't as bad as it was in 3.5, but it still exists.