It's a two part story:

1. The mobile market mostly targets kids and boomers and their resistance to microtransactions has been basically non-existent, making the market quickly become predatory and full of spam

2. Modern app stores have become abysmal, making it impossible for smaller games to see the light of day. 99% of google play is a dumpster fire, and the 1% that is decent isn't published by a multi-billion dollar company so you're unlikely to ever see it. There are good games out there, but the way the algorithms and ads work makes them constantly pushed down in the list. This isn't "a problem" to a company like Google because they're making bank off of all these ad spaces.

Anyways, most good games are paid, but here's a list of stuff I've enjoyed playing on mobile:

• Fancy Pants Adventures

• Bloons TD 6

• Dicey Dungeons

• Dead Cells

• Slay the Spire (but the mobile port is rough on small screens)

• Knights of Pen and Paper +1

• The Enchanted Cave 2

• Let's Create! Pottery

• BAIKOH

• Data Wing

Probably a lot more I forgot. Have at it.