If Bitcoin is a peer-to-peer electronic money system, then DeFi is a peer-to-peer electronic financial instrument system. The ecosystem of decentralized finance can provide anyone with access to traditional financial services, eliminating the need for intermediaries and lowering barriers to entry.
How useful do you think it will be in the future and will it be affordable for small investors?
i think you already pointed out the importance, decentralization, it is the sole purpose of blockchain, so defi is operating on the basis of decentralize finance in which the transaction is p2p and no intermediaries, if truly people are getting tired of traditional finance where people are mostly controlled, then i think soon the interest will rest more on defi projects, (the good and legit ones of course).