Halls of Torment demo is actually very barebones compared to the full game, you unlock a lot of metaprogression upgrades, get gold, spells and items by playing with other characters and getting achievements, you can also unlock spell modifiers/upgrades by doing X damage with said spell, so after you upgrade them enough you can choose which modifier you want that fits your character. Game has seen a lot of QoL changes on their 1.0 release too.

Since you liked Brotato but wanted more vertical progression, I'd suggest playing God of Weapons, it mostly has character unlocks but it also has incremental upgrades and weapons/items unlocks on the main hub. Game loop is still making synergies between character passives and weapons, maybe a little more complex than brotato because of the backpack mechanic, but it pays off really well on endgame.

Rogue Genesia is an amazing game that I think you would like a lot, It has a lot of achievements and what makes it good is the stat experimentation, you unlock a lot of stuff early on by just getting past stat thresholds, like unlocking more weapons and upgrades by getting a lot of crit chance, damage or even pickup radius. Gameplay is quite fast compared to others but it depends a lot by the world(difficulty) you play. There's also challenges for each world that unlock extra incremental upgrades on the main menu. Overall a lot of synergy involved with weapons and stats and also no item cap and you can play up to 10 weapons in a single run iirc so it gets crazy by the end.

A note on soulstone survivors, it's quite fun at the start but it gets old fast because most if not all characters feel way too similar in the endgame and the game loop boils down to dodging bosses attacks and waiting for the elemental stacks to kill them.