While this video is a bit uncomfortable to watch because pokes at the "blame Microsoft" thing quite a lot, I agree with the general sentiment.
One of the major reasons why Minecraft has been dying is, as this video mentioned, that "we all grew up". I used to play this game during my college days with a bunch of friends, and more and more of us started getting real-life jobs to the point where we just don't really have time for it. Outside of that, other games also feel more appealing.
Not to mention the fact that one might get overwhelmed at the barrage of new features from recent not-that-good updates, re-learning the game felt way too much of a hassle.
This comment sums up my views nicely:
While I may be biased because I still greatly enjoy this game the same way that I have for the past nearly 6 years now, I don't think that the game is dying simply because it's presence on YouTube etc is dying. I do however agree that the quality of updates has declined in recent years, but that's not due to Microsoft. It's important to remember that Mojang still have 100% of creative control over Minecraft and Microsoft is simply taking control of marketing and merchandise along with releasing versions of the game on various different platforms. They have nothing to do with Mojang kinda running out of great ideas.