I'm familiar with both those tutorials, and indeed have been programming the 6502 for 45 years (and Z80 for 44).

HOW is RV32I more complicated than 6502 or Z80? I sure can't see it, please explain.

There are more registers, but that's not complicated because they all behave exactly the same as each other (with the sole exception of the Zero register always reading as 0) and every register can be used for any operand of any instruction.