MIPS and SPARC blew everybody out of the water at their introduction, but they sacrificed elements of the instruction set for immediate/generational performance gains.
"RISC II proved to be much more successful in silicon and in testing outperformed almost all minicomputers on almost all tasks. For instance, performance ranged from 85% of VAX speed to 256% on a variety of loads. RISC II was also benched against the famous Motorola 68000, then considered to be the best commercial chip implementation, and outperformed it by 140% to 420%."
There were reasons not to use these architectures, even when/if open.