Libra has raised fears about the future of blockchain mainly because it goes against everything the community wants and believes in: decentralization.
Facebook could ultimately create a massive closed-loop revenue model from ads, digital marketplace, to payments. Do consumers want to bet on the status quo of existing monoliths?
https://elixxir.io/blog/is-libra-the-future-anyone-wants Indeed, almost all businesses get fierce competition. Moreover, online business competition is easy for everyone. But I think the blockchain system is still able to compete with Libra. Especially in terms of security that has been tested since the blockchain was born.