I find it essential to have a MIDI CC knob box of some kind with FM. My MPC works in this capacity, I also bought an external one. Most FM synths support a huge number of MIDI CCs and FM really comes alive if you twiddle with the knobs during patch design, same as with other synths.

This link is a great practical guide, which has you look at waveforms in an audio editor and clone them using FM, one operator at a time. He walks you through making clones of several real life instruments, 6 operators is enough to sound quite good and 8 is even better. FM has a reputation for being computer-y sounding but it doesn't need to be. A lot of that is just baggage from default patches introduced decades ago with that fresh '80s sound, those patches from the DX-7 are still on the newest Yamaha flagship workstations. And as everybody knows the grand majority of sounds you hear in music are barely- or not-tweaked presets.

https://csclub.uwaterloo.ca/~pbarfuss/FM_Synthesis_of_Real_I...