Fiat doesn't work on a finite planet. Crypto has failed on its goals. What is a better way to be economically secure?

Well, this is a fair criticism... of Bitcoin :)

It's supposed to be decentralized, but things like mining pools have lead to heavy amounts of centralization in block production. If we look at Bitcoin, for an example, we see that over 51% of block production is controlled by just two mining pools. That's not limited to just Proof of Work mining either. Proof of stake sees centralization in staking pools as well. That's only just looking at one aspect of the network

Centralization of mining pools (and mining in general) is indeed a serious problem. In Monero we now have p2pool which is totally decentralized. For now it's just shy of having 10% of total hash power, so there is a long road ahead, but we are moving there. ASIC resistant RandomX also helps to ensure mining decentralization.

It has also not really been seen as a currency. People's view of it as an "investment" which have the opposite qualities you really want to see. People are encouraged to hold it and never let go, meaning they won't want to spend it which is adverse to its use as a currency. This has also lead to it being incorporated and dominated by the very financial systems it was initially supposed to move away from

I don't think this applies to Monero, which is more or less the only currency used in DNMs.