You may like BlazBlue Entropy Effect. It plays very much like a 2D fighter, but has roguelike elements like upgrading of moves and meta-progression after each run. Instead of fighting other players you fight cpu enemies.

The most extreme example within your parameters I can think of is vampire survivors. You don't do anything but move your character and pick upgrades

Looking for those as well, only thing I found was BB:EE, Ultra Age's roguelite mode, Nioh 2, and the upcoming Morbid Metal. To some extent, Godfall, Kingdoms of Amalur and Wayfinder.

I want a grinding game where you get exciting loot, with combat like DmC to master. Those basically don't exist, so you have to settle for better combat with some loot upgrsdes, or deep rng loot chase with more basic combat. Roguelite games with deeper combat is probably where most of those games will live.

That said, Nioh 2 is really the best of both worlds in late game (Diablo look with the best "grounded" combat ever, just harder than Souls games for your first 30 hours).

https://store.steampowered.com/app/1942280/Brotato/

This might be in line with what you want, and its only $5

Absolver might fit the description, 3d fighting game but you learn the moves by blocking or dodging then defeating NPCs and PCs. It's not super long unless you try to learn all the styles and moves or I think they added an infinite dungeon, not sure how good that part is since they added it after I played. But even if you don't like the PVP the single player learning the moves and defeating the bosses and big bad at the end is really fun.

Risk of Rain is like this (1 if you like 2D, 2 if you like 3D games). You constantly buy items and they stack like crazy. You either don't stack fast enough and die or manage to overcome the hurdle and become a god

Mothergunship is a FPS roguelite, where you get to build awesome-stupid looking guns between runs, getting temporary upgrades while blading everything. It often goes on 80% sales on GOG and Steam

Others mentioned brotato and vampire savior, there are several similar games like them nowadays, you can check their tags to look for more on Steam

Elder Scrolls Morrowind has janky as fuck combat (hidden dice roll to check if you actually hit) and the only way to get better is with higher numbers in your skills and attributes. You can use magic and potions, both of which you can make yourself, to boost yourself to godlike levels

Dynasty Warriors 8 offers several weapons for the characters, plus it lets you equip skills to make some actions better, like higher attack and higher attack while mounted. As soon as you learn how to block for quick camera turns, you've mastered the game

Like, Deus Ex?

For local multiplayer, Rounds with mods. If you mod in new cards/powers and turn on endless rounds, the powers inevitably become game-breaking in unique and hilarious ways after 10-20 rounds of stacked card power-ups.

You should def checkout “Death Must Die”. You basically move around collecting upgrades, auto-killing hordes of enemies, and when you level up you pick one of three buffs/abilities from one of ten gods. The buffs/abilities have both ranks and levels. There are 3 acts to play thru each with different mobs. After you beat all 3, you can add more effects to mobs to increase difficulty and rare equipment drop rates. The acts have a 20 min timer, but of course it pauses when you’re choosing buffs or the game is otherwise stopped. There’s six characters to pick from each with unique a talent tree that enhances your playstyle.