I think the main reason Nemesis gets more hate than the other TNG films is that it is at least partly blamed for killing (or nearly killing) the franchise. Horrible box office and all that. I think another reason is that they didn't seem to learn from their mistakes from the previous three movies.
To me, Nemesis isn't any less stupid than any of the other TNG movies. They are all very contrived and sloppily written. The plots in all four movies require you to turn off your brain for large chunks. They all contain extremely out of character moments and stuff that seems to contradict what was established in the tv show. Most of the complaints aimed at Nemesis could be said of the other 3 TNG films as well.