An FPU coprocessor doesn't make an 8088 run any faster, it only accelerates computation of floating-point calculations important for a subset of software.

The original DOOM used fixed point math so it could run on machines lacking an FPU like the 386 and 486sx. MSFS 1.x to 5.x didn't require a coprocessor either. Falcon 3.0 and related sims (MiG-29, F/A-18) likewise require only a 286 but could use it optionally.

Here's a approximate list of x87-usable (required or optional) software: https://ctrl-alt-rees.com/2019-06-06-list-of-software-that-u...

R:Base System V port to OS/2 (FPU optional) was basically a rewrite from FORTRAN to C, and experienced issues due to Microsoft's substandard floating-point emulation library compared to the one(s) Microrim used previously.