I will remind you that these DEFI were building inside the major platforms. I don't see any reason for the bitcoin to be replaced by defi coins. It looks like you must see it from the technical view too.
DEFI is not having the main aim to replace any other crypto currency.
They are not going to take over in fact they are going to supplement the technology and the community of Cryptocurrency, it has usage it had features and it brings something to the table Defi is another niche that is going to help adoption and we should be excited about it and support it.