The FOMO argument is exactly what was used by banks in GFC: as long as the music is playing need to dance.

But current era also has echoes of capex financing (eg cisco lending to its buyers) and Enron (eg use of SPVs).

I don’t think that most people who are concerned about a bubble think people and orgs fueling it are stupid, but they’re operating with local incentive structures that can result is systematic problems.

And for folks who have lived through multiple of these (and maybe lost paper wealth, retirement savings, or homes), I think being concerned is reasonable.

Hard won lessons and all that.