This is the correct answer I think. They’re also not interested in releasing sub-par games, and again like you say they don’t need to release games at all to make money anymore. So if they’re not that interested and haven’t come up with anything conceptually/mechanically that reaches the high bar they’ve set for themselves, it makes more sense to scrap/postpone.
Their reputation is much more important, and they’re just not going to half-ass Half Life 3. It will come out when they feel they have something truly extraordinary, or it won’t come out at all.