FOMO just means “fear of missing out”. It is indeed usually used disparagingly in the sense that the person feeling the fear needs more backbone to just ignore the ad, but presumably the person feeling the FOMO rather than using the pejorative “FOMO” might not necessary think in those terms
I imagine the pythonistas who think pattern matching is stupid shit are saying python has developed a case of “FP envy”, and pattern matching is a passing fad. But presumably the people pushing the proposal (unless they are super cynical) think the pattern matching is actually good!
That is a complicated question that best be taken elsewhere. But I invite you to join me down the Post-Keynesian rabbit hole :).