That's basically the RISC approach, using simple one-clock instructions instead of complex microcoded instructions. In the case of the 8087, it made sense to use microcode because the 8087 is running in parallel with the regular 8086 processor. If the 8087 is constantly fetching micro-instructions from RAM, it will get in the way of the 8086. (Note that RISC chips rapidly added floating-point units, even though that goes against the strict RISC ideology.)

This is also why RISC would never have happened if it weren't for the fact that, for a brief period in the history of computing, RAM was faster than the core. Single-cycle instructions only make sense if the fetch can keep up.