The biggest sources of skeptism were around logistics and value as a currency:
Is there a cryptocoin that has successfully solved logistics without disastrously failing as a currency?
Even if you ignore the environmental aspect... has any coin that has achieved scale not experienced deflation that would make the Great Depression look like a hiccup?
To me the skepticism has always been "you can't have a functional decentralized currency". Some people take that at face value and proudly proclaim "people will accept your BTC/ETH/etc."
But most people mean it in the sense we think of currencies belonging to non-failed states: aka being a somewhat stable store of value. More widely used for payment of productive economic output than fraud and speculation...
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I see crypto as I see Tesla, maybe there way a point but it's long buried under the mania.
Disclaimer: Due to that mania I keep some as hedge, but again, imagine saying I keep dollars under my pillow as a hedge that next year they might have 10x'd in value...