I've been speaking to the guys from New California, and their reason to endorse Vortex was that it was actually capable of handling their ~7gb mod installation, whereas NMM is infamous for having trouble with large files.
We have stopped supporting NMM quite a while ago, not just since the Vortex beta was released. NMM is still available, you can still use it, and there is a community supported version on GitHub. We are not hiding that fact, and we are not forcing anyone to switch over. The link to our last NMM version as well as the GitHub build is on the Vortex beta page itself.
That being said, we are certainly not pushing mod authors to stop supporting NMM either.
Lastly, calling Vortex trash might help to vent your frustration, but it is not particularly helpful when it comes to us trying to improve Vortex going forward based on user feedback.