Hi
I'm just making the switch from 1.12.2 to 1.15.2 at the moment and 1.15.2 seems stable enough to me. I've had no trouble with gradle build in IntelliJ.
I suggest you use the latest "1.15.2 - 31.1.46" instead of recommended "1.15.2 - 31.1.0" because latest uses a much newer set of MCP mappings (i.e. nearly all the classes and methods have sensible human-readable names now, whereas recommended is still full of func_923535 and similar names).
-TGG