I think that there are two points to consider about Libra:

It will not replace steem

Since Libra will be a kind of stable coin that will be linked to the value of fiat money, it will not be possible to create value from a reward pool like steem. So users won't get rewarded for their posts. Libra will rather be a means to transfer money from one user to the other.

Steem offers exactly the same for three years already, but lacks one incredibly important thing: simplicity.

I think that you point out the most important "problem" about steem. It is simply too complicated for new users to understand and to adopt.

Crypto democratized

What we should understand however is that libra will be like an entry door for people to the crypto world. When you take all the users of facebook and instagram and that you offer them an entry door to the crypto world, this will contribute greatly to make this world accessible to them. Imagine that you can promote steem to facebook users who are already familiar with another form of cryptos (libra)....