But with bitcoin you can't loan money that doesn't exist.
Bitcoin will never replace FIAT. They'll coexist. If bitcoin will be deemed as the only currency that we can use then lending is possible. People will always try to find ways to lend out money. How can we use bitcoin as a mode of payment if it doesn't exist?
Maybe not, maybe it will but the point is not to implement bitcoin to our current system but manage to implement our system into bitcoin. We are not here talking about how bitcoin can be good for the world because it is the perfect side dish to it, we want it to be the main course. Bitcoin and crypto in general with the help of blockchain powered world could change the way we live and change the way economy is distributed.
Rich are too rich and poor are too poor in this world, crypto is here to prevent that and help close that gap between the wealthy and the unfortunate. Plus the blockchain could have so many uses in politics that eventually people will see politicans for who they are and decide to vote for the pure person instead of corrupted one. All these combined can make bitcoin a bigger player than just implementation to our system.