Facebook doesn't want to disrupt financial system, it wants to become a part of it. They use Libra to achieve this because they want to ride the cryptocurrency hype, but they can't hope to use it as a loophole, the reaction of regulators and government showed it clearly.
But the biggest problem of Libra is that no one really wants it, there's no good reason for people to use it - it doesn't have convenience, it doesn't have any properties of cryptocurrency, it doesn't offer customer service like banks do and so on.
Exactly. Facebook's Libra cryptocurrency cannot disrupt the financial system because it's merely a stablecoin backed by the value of the USD. With extreme centralization, it's just another central bank. If they have the desire of becoming a worldwide currency, they could easily provide customer service like Banks do, among other things. Once governments approve the launch of Libra, Facebook will be registered as a financial institution like traditional Banks.
Despite this, Libra will not entirely replace existing Fiat currencies because of many obvious reasons. Central Banks will always remain in power, and will try their best to prevent any other alternative (like Libra) from taking over the world's economy. Which is why, Libra's prominence within the mainstream world may be extremely limited in my own opinion.
In the bright side, Libra will trigger massive adoption of Blockchain technology if it becomes a success. Cryptocurrencies' popularity will rise like never before because of this. In the end, our finance will be disrupted by Blockchain technology itself instead of a single cryptocurrency. Governments will devise their own currencies that use this innovative technology in order to change the world for the better. Both Libra and crypto will do fine as alternative money in regards to Fiat for a very long time. Just my opinion