There is no doubt cryptocurrencies gained a huge share of relevance over the last years. Let's put aside the question, if the overall market cap (~ 500 billion) of those about 3K cryptocurrencies is somehow real or not. The new possibilities and organizationals cryptocurrencies implicate have positive impact; cryptocurrencies for sure have a lot of strengths. But as with every (rather) new technology there are weaknesses. Three of those seem to be especially relevant:
- Tangibility, transparency and usability: Cryptocurrencies are not easily understood, which is not only true for laymen. Besides that the ecosystems around cryptocurrencies are not too transparent, especially for laymen. Finally cryptocurrencies aren't really easily usable; more or less an implication of the above.
- Cryptocurrenices are highly inefficient: The price for the strengths cryptocurrencies implicate is inefficiency. This is due to their basic design (decentral p2p, trustless) and and their major way of implementation regarding money creation and basic modus operandi (Proof of Work (PoW) (Wikipedia)). This inefficency is directly linked to real world resource usage: It is fair to see the energy balance (Wikipedia) of for example Bitcoin as disastrous.
- (Transactional) Capacity: Also due to 2. the capacity of cryptocurrencies is rather small, the throughput per second isn't particularly high. Bitcoin for example experienced long wait times and high transaction fees recently.
Those points sum up to one consequence: Cryptocurrencies are not for the mass-market.
Maybe even more important: It is even not desirable, that cryptocurrencies will be for the mass-market, if you look at energy efficiency.
Actually there are ongoing discussions, if for example Bitcoin should be positioned for the mass-market at all. Or if it rather should be position itself as a service for large transactions in B2B only. With that said: All those weaknesses (and more) have been identified and get discussed or are being worked on by real implementations (for example cf.: Proof of Stake (PoS), Bitcoin Cash (BTC) (Wikipedia)). There is no doubt, that the cryptocurrency community is highly active and capable.