The main factor that can make long term crypto is the number of users who continue to increase, if there is no user then it is certain that crypto can not survive, and of course to make users want to use crypto then have to get profit.
In order for cryptocurrencies to exist we do not necessarily need a growing number of new users, what we need is that the current users do not abandon cryptocurrencies, also you do not need to give profits to those that are holding crypto, what you need to do is to offer them a valuable service or product, and bitcoin is already doing that it allows to you to send money all over the world in a matter of minutes without a third party.
Crypto is very promising investment and I believe this is design for long term to make it more profitable because i believe at the early stage of crypto is very volatile.