1. React may have been developed by FB, but they no longer really own it. They released it to the open source crowd. If you're concerned at all about privacy, you have no need to be.

2. React apps are fast enough. Maybe some things are faster, but the differences are negligible for most apps. So much so that it hardly really matters.

3. RAM usage can be disputed easily enough. For most projects this is a non-issue. For the times that it is, there are fixes.

4. As others have mentioned, this article is indeed BS. It sounds to me like you've very little experience writing React beyond just to try it out. Again, gain some perspective.