Game engine and combat system are great, but the implementation is crippling.
The game does not pause when you open menus to upgrade stats or read what your items/abilities do. There are no safe areas, except those achieved via spawn manipulation. Enemies appear from nowhere in huge hordes constantly all of the time starting from about two seconds after a run starts.
Nevertheless, the way to play the game successfully, presently, is to camp a torch in a corner with a ceiling, thus maximally limiting enemy spawns, and grab whatever items come your way from the trickle of enemies quickly buying up your stats to absurd levels in between waves, then rushing the torches rapidly killing all the bosses in sequence via your absurdly powerful attacks, spells, and items. That camping and super-cautious play requirement kinda conflicts with the no-holds-barred constant enemy spam insane rush the game seems to otherwise be going for. But you can't have non-stop brutally difficult combat and require players to try and read what their abilities do and manage an inventory while simultaneously doing that.
What I would recommend is to disable item configuration and stat leveling most of the time (let players still pick up items and spells, and cycle spells the same way they do currently) but give the player periodic rest stops to configure equipment and spells and stat points and what not in. Perhaps the player can initiate a rest manually at lit torches as long as there's no boss active, or perhaps killing enough enemies in a short enough time could spawn a miniboss which when slain makes the enemies flee to regroup and gives you the rest opportunity, or perhaps you could create makeshift bonfires to keep the enemies away with light temporarily while you rest or something. In any case, explicitly separating menus and reading from the fast-paced combat would massively improve this game, I think.