I'm not really opposed to the idea of cryptocurrencies. I think being able to exchange value without having to go through any middle-men (i.e. banks) could be valuable. It's kind of like cash in that sense but digital.

I am however very opposed to the execution so far:

1. Wasteful proof-of-work algorithms that spend way too much electricity.
2. Treating them more as ~~stocks/investments~~ gambling instead of as an actual currency.
3. New cryptocurrencies seem to crop up every day. This is more of a pyramid scheme than actual innovation at this point.

If those three improve, then maybe it will actually be okay. It's unclear whether (1) will happen ever, as anyone leaving the proof-of-work cryptocurrencies behind for other less wasteful ones just make mining more valuable for the ones that are still mining the proof-of-work currency (as far as I understand). But maybe it will eventually be better, though it doesn't seem that way right now.

(2) happening is a little more likely - it would likely slowly happen if people started using it for actual payments and goods. If goods had a price based on a cryptocurrency, the value of the cryptocurrency would be more stable (I would guess; disclaimer I am not an economist or anything like that). But still, this is not too likely to happen, at least it hasn't happened yet in any big way.

(3) is also problematic and not likely to change any time soon. It seems like we will never agree on using just one of the cryptocurrencies and if we don't, I can't really see it taking off.

So generally, unless something changes with how cryptocurrencies are currently handled (ironically, maybe nations need to step in and "bless" a single one for anything to change), I don't really see a bright future for cryptocurrencies.