why I don't like crypto, ethically, financially and technologically:

proof of work mining (e.g. Bitcoin) wastes ungodly amounts of electricity (until the world is 100% renewables mining displaces more useful work and thus creates emissions) and computing capacity
proof of space is the same but for making the world a worse place by driving up storage costs for everybody
coin speculation is a massive ponzi scheme and no crypto fan acknowledges this
the e.g. bitcoin network throughput is ~dozens of qps which would merely be hilarious if it wasn't burning as much coal as Australia
just on pure waste: Bitcoin production is estimated to generate between 22 and 22.9 million metric tons of carbon dioxide emissions a year, or between the levels produced by Jordan and Sri Lanka, a 2019 study in scientific journal Joule found. (source) - ie this game is an entire additional country of environmental damage for ~no useful gain
no one has found an actual use for any of it except for online drug dealing (which requires niche coins since Bitcoin is massive distributed public ledger)
the level of market manipulation and accounting fraud by eg Tether (and now USD "coin" admitted lying about the backing) would normally send people to jail but has for some reason got a free pass
the clueless marketing by fanboys who only hope to enrich themselves by creating another layer to the pyramid
the endlessly stupid projects it has spawned where blockchain is seen as a solution to anything aside from the niche case of "distributed tamper evident journal"
it has single handedly made mass international ransomware a viable business model by allowing a way to receive cash outside the banking system
the general enablement of all sorts of scams, e.g. the endless kids on this very subreddit promoting "12% crypto savings accounts"
It isn't nearly as secure as people think it is. Any determined state actor could subvert the network.
Deflation isn't actually a good thing in a currency. It ultimately favours the wealthy who can hold and dont need to spend.
Mining (proof of stake or work) allow the wealthy to invest in mining equipment to control or dominate the market.
Ultimately, no government on earth is going to give up its monetary policy as that is a key lever of control.
essentially everyone involved at this point is just trying to hustle the next generation - any hope any of it would serve as a useful technological or financial system has gone)
the massive mis-represnetaion of how bitcoin in particular works, despite claims, it does not offer any of the following:
anonymity - the entire blockchain is public and diligently recorded on millions of nodes
distributed freedom - a small number of mining cartels control almost all the hash power and normal people use one of ten crypto currency exchanges for everything anyway
unencumbered transactions - it's comically slow and inefficient
convenient purchases - wallets are unwieldly for normal people, no reversibility
store of value - volatility is hilarious and all anyone cares about us BTC:USD
things I do like about cryptocurrency:

monero is pretty clever
ethereum smart contracts are pretty scifi
watching people learn 5000 years of history of why we have banking regulation in a single decade has been fun
there will be some massive financial catastrophes to watch that will mostly only harm people who did not read my previous list
the earlier state of every single exchange either getting robbed or exit scamming their own fanboys was quite funny in retrospect
(thx to u/TwentyCharactersShor for some extra items).

I used to just think cryptocurrency was a fun hack but a bad idea for the mainstream, but I'm now pretty convinced it should be banned purely on resource grounds, since it seems impossible to force the externalities to be addressed

It's possible that someone will invent a cryptocurrency that's efficient to a level that it's not morally reprehensible to use, but how would it take off? the existing cryptocurrency interests want bitcoin to succeed purely because they're the top of the pyramid and also selling the shovels and so now anything new has to compete aginst the real financial sector and the entrenched cryptocurrency players.