Skepticism might be warranted, but it should be noted by now that decentralized finance has a place in the present and future of our planet and it's not going away. I strongly encourage technologists to keep an open mind and do in depth research into the space. Yes, 2017 was over-hyped. The tech was not mature then, and while it has matured some since then, there's still quite a ways to go. Bitcoin Lightning network…
The problem with decentralized money is that there is no way to manage the supply - you can only commit to a given supply curve, but you cannot adjust it according to the state of the economy. Money is a collective action problem, a public good - it requires a solution that bounds everyone - just like defence.
Why do you think this? Ethereum has changed its inflation schedule a few times recently.
It seems you are basing this on the hard capped supply model of bitcoin which is not the same as every cryptocurrency.