I just want to find a secure and decentralized alternative to bitcoin
Which blockchain could become just as decentralized as Bitcoin?
Where could I store my assets in an emergency if there are no more bitcoins?
But why? You won't be able to find anything similar to Bitcoin. No shitcoin can compare to King Daddy. All other cryptocurrencies were created to imitate Bitcoin and/or make their creators rich eventually. So it's impossible to find a secure alternative, it's only a matter of time when the rug will be pulled.