> There’s really not much question we are in a giant bubble

IIUC, some indicators correlated with previous bubbles are lighting up now, which is being interpreted as evidence that AI is likewise a bubble. But what about indicators of previous non-bubbles? How did it look when textile mills were first industrialised, or kerosene replaced whale oil for lighting, or the electric grid became widespread, etc. -- real advances that materially increased productivity in a lasting way? If these same indicators lit up in those cases too, how can we distinguish bubble from genuine advance?

A number of things were both: the railway bubble was pretty bad for investors even if railways were a genuinely transformative technology that remains in use.

https://en.wikipedia.org/wiki/Railway_Mania : for "railway" substitute "data center".

I just don't think AI is any of those things. I understand that my argument is anecdotal and qualitative, but I just don't see AI (LLMs) materially increasing net productivity in the economy.

1850-1929 was filled with absolutely spectacular boom-bust cycles. Something working long term and having a bubble and crash in the short term are not mutually exclusive.