My first reaction is their reasoning is a load of fucking bullshit. If they were truthful and said, "we didn't make it because we didn't want to and we let the creative people who guided the whole thing leave," I'd understand. I found it interesting that most of the interview was about Gabe Newell becoming interested in UI interfaces and how sensations that affect the brain more so than his wanting to actually make games anymore. Judging by his response to his favorite game from last year, he is not interested in keeping up with that anymore. The guy who helped on Alyx was more enthused to talk about that.
They talk about their failures (Artifact, Steam Link, etc) and how Gabe views making games as working under a deadline as a product of "regrets and mistakes" when they can't even get Steam to have decent customer support.
I think it's just Gabe Newell deciding he doesn't want to do another Half-Life because he's tired and he's gotten lazy and he wants to do something else. He was more happy with Portal 2 because he didn't have to be directly involved and make those kinds of decisions.
As long as he's alive, we'll never have Half Life 2 Episode 3 or Half Life 3. Honestly, I would almost prefer at this point that we didn't. Valve will make whatever they want with Half Life they feel interest them, not what people expect or provides closure on the series.
