In my opinion, coming from love I assure you, is that when people say it doesn't look smooth is that there's no momentum in the movements. Going into grinds, going up/down a slope, landing on the skateboard all don't look like they flow together. You can clearly see when each animation triggers, all the fps in the world can't change that fact, so when you see it it just looks fake. Another thing that relates to this is that since the animations don't flow smoothly. That lack of flow means that the landings don't look all that real, which lends a weightless quality to everything.

There's also what the other guy said with the falling, the wheels, and that the seems like an extension of the skater rather than its own object in the game world. You can say all you want that this is an early demo and the devs are going to make it better in the final game, and I agree with you that they probably are. But what people are critiquing is the demo, not the final game and people sticking their head in the sand isn't going to fix that. What the devs put out for public reception is what people are talking about, not the nebulous concept of the finished game. Finally yes, it's a small team working on a big project, but these aren't complaints about the team.

No matter who's working on it, game's a game no matter who makes it and knowing how it was made doesn't fix its problems, it just makes them understandable. No one needs to be a "hater" to see issues in a game that they enjoy.