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 Libra is another type of stablecoin according to source, but there are lots of stablecoins in the market, and they are not a threat even to world financial systems, maybe it can help to ease the transactions unlike using the banks which require higher fees and a transaction time.
Though some people might say it doesn't pose any threat to the world financial system but politicians are still putting their attention into it since facebook is among the biggest company in the world. if it is USA, I'd guess that they will definitely take some action into it.