Usually DeFi is a utility token or dApps which have some finance function.
So, it has to built on top of dApps platform like EOS, ETH, DOT, CLO, ADA or another platform that have capability for it.
By that fact, its impossible a DeFi replacing ETH.
that's why ethereum was providing an infrastructure for defi to run on ethereum blockchain. People didn't aware about this and they keel call that defi is comparable with ethereum while the fact was saying the opposite thing than it.
it will never happen and basically OP didn't know what he was talking about that. It looks like he must learn what definition of defi and blockchain.
Blockchain as the basis network to run the defi platform can be categorized in the different thing.