This is only my second Monster Hunter game (first was 3U on Wii U / 3DS) and I'm absolutely loving, but I was already pretty I would.
I don't think you have to worry about the game, it has sold 6 million copies by now :-)
About grind and time spend in MH - and a thing that is quite different from most other time consuming games - is that the "curve of experiences" is absolutely linear.
The monsters will get tougher, but the details of the game remain the same through out.
This is contrast to something like Destiny, which I also enjoy immensely, where you're grinding to get to the end game and working to be able to do the "real content" like the raids. Just like most MMO's.
This makes me feel that I haven't wasted my time with Monster Hunter, no matter how much or how little time I've spend.
Holy smokes, 6 million! Awesome.
Thanks for the great comment @floede! I've also been meaning to check out Destiny.