People are throwing stones, but I suspect you didn't mean mature but perhaps "modern"? RISC-V doesn't carry all the endless legacy of 30+ years of MIPS variants and is in most ways cleaner and more streamlined (I do fear RISC-V is rushing towards its own mess, but that's another story).

MIPS (the ISA) _could_ have had RISC-V current position but I don't think MIPS (the company) could have survived. Whether the Phoenix can survive this reinvention remains to be seen. It's a very crowded space, especially for in-order processors.