Lifecoach recently took a "break" from the game and was critical with some of the decisions that Valve made. He'll probably be back, but he's done/said the same things when he quit HS and Gwent.
An interesting comparison I read is how similar it is with Titanfall 2. Both games were highly praised by people who played it, but their numbers dropped off pretty quick after launch. A possible reason is that since the games have a very high skill ceiling, each match can be very stressful and intense. Most gamers probably play games to relax and have fun, so when they find time for gaming, they may gravitate towards something that's not as brain intensive. I know for me, after a few matches in Artifact, I'm done for the night. Saying that, I don't think this game is dead at all, but I really doubt numbers will improve that much unless Valve makes some serious changes with the core gameplay.