I completely got the trepidation of the Black Mesa team when it came to Xen: The original was complete shit.
This however, looks like a great effort:
https://youtu.be/TAIJich73NY
My biggest criticism is a couple of talking heads repeat the axiomatic 'singleplayer is dead' in the segment about HL3. One of them was a Black Mesa developer, which to me just seems bizarre.
It would be more truthful to just admit that studios aren't interested in single player because it is hard, and hard is expensive.
On the subject of Half Life, I really enjoyed this documentary: https://www.youtube.com/watch?v=BQLEW1c-69c