I could go through each of your concerns, but I’ll just leave it at two:

• rich get richer - someone needs to be trusted to confirm transactions properly. Requiring some skin in the game (proof of stake, mining, etc) with a reward is the way to do it in a trustless system. This exists in fiat currencies as well, with the main winners being banks and large borrowers, so I don’t see it as a serious issue.
• energy costs - mining cryptocurrencies has a high initial energy requirement, but it scales really well in terms of transactions, so if transactions double, we’ll see a modest (way less than double) increase to energy usage of the network as a whole. And in theory, mining operations would prefer cheap power, so that means whatever excess green power exists that would otherwise be wasted worldwide. There’s an ethical option to mining energy usage.

The reason I’m not going to go through each is because each problem has a solution, whether that’s in an already existing currency, or will go away as it scales.

Here are the real problems as I see it:

• way too many scams - which leads to…
• way too much volatility - most cryptocurrency users are speculators, so there’s…
• no mass of regular transactions to attract vendors

Even if we get past the FUD, we’re still going to have adoption issues because of the above. And I don’t have a good solution for that, but we need adoption to stabilize the currency and motivate solutions for problems.

I like the idea of cryptocurrencies, but we need a large institution to normalize it before people will adopt it, and I don’t see that happening. Maybe stable coins are the way forward, IDK.

One thing I’m interested in is GNU Taler, which is a relatively simple digital transaction system that preserves payer privacy. If we could get a big institution to use it (e.g. Mozilla for micro payments to websites), people may feel more comfortable experimenting with digital currencies.