Every hunt is different honestly, it's grindy in the sense that you hunt monsters and little else, but the challenge makes it really addictive IMO. Of course, if it isn't for you, then it isn't for you. I personally hate grinding, and I hate turn-based RPGs, but Monster Hunter is my favorite game and it's got both grinding and turn-based combat (in the sense that if you don't follow the rhythm of the monster, you'll get your ass handed to you).

Watching gameplay is a little flawed since it's very much about the feel of the game, the weapons, the hunt itself. If you can, give it a try at a friend's place or something, or get the demo if it's still up. I've only played 4U and Generations (outside of World), and have around a thousand hours (about 600 in 4U), not just because there's a ton of content, but because you just get so caught up with farming gear and completing challenges and attempting speedruns and trying new weapons. Each weapon is an entirely new playstyle, too, so it's hard to get bored of the combat.

World is thinner content-wise than previous games, but they've stated they'll be beefing it up with additional content down the road, and there's more than enough to sink your teeth into at the moment.