What irks me the most about this is his use of anecdotal evidence for his main point: he spoke with a couple people that said they do not enjoy 100% completion but do it anyway. Me, my 2 best friends and girlfriend all play pokemon and all enjoy getting 100% of them. Yes, this is anecdotal too, but now it's at least just his word verse mine.
Catching them all is a social experience for us. We all look at them and admire or mock the designs and descriptions of them, trading them around like baseball cards while somewhat racing against each other to see who can finish first. We also try to make the strongest team, catching the specific type of a species with perfect nature, moves, IVs, et cetera. We have fun. Pokemon is designed for people like us and younger kids that are in school and it can give them a common topic to talk about, trading around and making friends when they otherwise wouldn't. Helps geeks meet other geeks, haha.
Yahtzee really should stop reviewing games in genres he doesn't like. As he said, people play games for different reasons, and if a genre doesn't appeal to you, it isn't fair to review a game in it. Stick with action-adventure and horror games, those are his better videos. So many of his complaints about pokemon show just how much he completely missed the point and didn't get it. It would be like me trying to review a sports game when I don't like sports. It isn't fair to the fans and it isn't fair to the game.