I'll admit I was also massively disappointed with the last FX generation (BD/PD/SR), but I will also admit the design was interesting and, although futile at the end of the day, did bring AMD some important lessons to be had. Specially when betting so much on Speed instead of IPC. The modular approach, I still find fascinating, even with the shortcomings for real world usage, but I can absolutely see why it can work, under a brainiac uArch, in server workloads. While Ryzen's SMT current incarnation is great, I believe "modules" is still better (when done correctly) for specific workloads.
In any case, I skipped the FX generation and only built 1 PC for a friend to experiment with it. While I wasn't massively disappointed with the performance, the shortcomings of the CPU were obvious. The only good thing about FX was that, at the bottom, they offered decent performance for a really low price. The FX4200 was decent, but really un-remarkable. Same with the APUs based on FX and kind of ironic... Where you need to save power the most, you put a power hog next to the iGPU... Some great thinking process there, hahaha. Anyway, that desperation brought AMD to the current power saving techniques they applied to Ryzen, so that's what I meant by "lessons learned".
Cheers!