It all comes down to how you define Decentralized Finance. You could put Bitcoin and what it offers under the category of "Decentralized Finance" and it does offer a solution for the "unbanked".
The unbanked are people who have issues to access bank system and can not have their bank account. They can have their own banks with Bitcoin with very simple condition nowadays.
Have Internet connection, and a device to download a Bitcoin wallet, create to use.
It's worthwhile to note to be their own banks with Bitcoin, they must.
- Use a non custodial wallet, open source.
- Verify it, to avoid phishing, fake wallets.
- Backup their wallets.
- Test backups for recovery.
- Fund that wallet with Bitcoin and use it to store their bitcoins, to broadcast bitcoin transaction for their trades.
The problem is when these days people talk about "Decentralized Finance" they are referring to the DeFi token creation hype where they create an utterly useless token on a token creation platform like ethereum and pump and dump it. That's not Decentralized Finance at all! That's more like selling dog poop in a pretty bag!
A project that is centralized in Vitalik hands, was premined and was rolled back like Ethereum blockchain, is not a decentralized project and blockchain.
If Ethereum can not be decentralized, other altcoin projects and blockchain are only more centralized than Ethereum.