Environmental Impact: Bitcoin alone, has the environmental impact (Co2 emissions) of some small countries. For a 'currency' that is primarily used for stored value, not transactions, this is incredibly problematic. Assuming there will be no transformational breakthroughs in computing efficiency, proof of work is going to be with us, and obfuscating the long term value of crypto. - https://news.climate.columbia.edu/2021/09/20/bitcoins-impacts-on-climate-and-the-environment/

Complexity: My smart, non-techy friend literally just put 40k into Titan's crypto fund because he didn't trust himself to not make a costly error in purchasing the coins I advised him on. He's in his early 30s and works for a tech company, still not confident of transacting in the coins themselves. That's going to continue to be a problem of broad adoption.

Scammy coins: This thread loves to shit on Elizabeth Warren for trying to regulate the crypto space, I think her heart is in the right place, but often gets the details wrong - BUUUUUT if we want broad adoption, we need zero news stories of people getting rug pulled, hacked, etc. Regulation specifically around verification of project fundamentals would be incredibly valuable to giving consumers confidence in what they're purchasing, prevent people from being rug pulled and becoming a crypto detractor.

Little/edge case consumer utility: Self explanatory. Until there are actual broad consumer market applications we're all still rolling dice in a casino.