You're right that a lot of indie games are metroidvanias or roguelites. However, AAA games exist on an incredibly narrow scope these days too. You have shooters, sports, open-world action games, and that's basically it. Rarely do you see big studios deviate into unknown or experimental mechanics.

Indie studios have produced a lot of games with varied mechanics that are just a huge breath of fresh air for me, personally.

You'd never see a AAA studio making Factorio or Satisfactory, for instance. Probably unlikely to see them make a game like Darkest Dungeon, or Don't Starve, or Stardew Valley or Terraria or Starbound or.. the list goes on. You just might have to look a bit deeper to dig through the roguelikes and platformers.

A little reductive I would say? I would add at least:

* Puzzle (The Witness, Baba is You, Antichamber, Manifold Garden, ...)

* Survival/open-world (Minecraft, Terraria, Don't Starve, Subnautica, The Long Dark, ...)

* Horror (Amnesia, Outlast, Layers of Fear, Five Nights at Freddy's ...)

* Management/simulation (Factorio, Stardew Valley, Kerbal Space Program, ...)

* Metroidvanias (Cave Story, Hollow Knight, Ori and the Blind Forest, ...)

* "Walking simulators" (The Stanley Parable, Gone Home, Firewatch, ...)

Some of these maybe you'd disagree with (Are Metroidvanias just platformers? Can Minecraft still be put on a list of indie games?), but I personally think it's a crime to omit at least puzzle games and survival games. The offerings from the AAA space for those is not very impressive compared to the indie space.

There's tycoon games and strategy too. Stardew Valley and Rimworld are at the top of their genres. And games like Dominions, Telltale games. Horror might be up there.

Do we count mods? DotA and CS would be indie if so, but are now quite commercial.

This isn't true, there are plenty of trivial examples to counter this notion.

e.g. Annapurna Interactive has been publishing AAA-quality titles from indie devs for a long time. And most of those games don't fall into the roguelike or platformer vertical.

Roguelike just means you can beat it in one sitting now, which is a very good niche for indie games if you think about it. Slay The Spire, FTL, Rogue Legacy, and For the King are all "roguelike" but fill completely different niches in terms of actual gameplay and features and all are awesome.

There is no storage of indie RPGs and survival-style games either (e.g. Disco Elysium, No Man's Sky, Valheim)

That's not true. Microprose is back and have a lot of indie developed titles coming out this year. They are almost singlehandedly bringing the wargaming genre back from the dead.

I wonder where do Paradox strategy games fall, Crusader Kings / Europa Universalis ones. They definitely don't look AAA, despite offering a very deep gameplay.

And shoot-em-ups and beat-em-ups. It's what I mainly buy on my Switch when there are sales.

But yeah, not many games between AAA and indie. :(

Donut county, poly bridge, angry goose game.. I’d say there is way more variation in indie games

Don't forget 20 survival games per year.