I felt like the show picked up some weird pacing problems near the end of their senior year of high school and that those pacing problems bled over into the college years. In the earlier years, relationships moved really slowly. Stories focused on relationships and tensions that had been simmering under the surface for years. For example, from day one, the show did a good job of making me feel the tension between the Potter girls and their dad, so whenever he was in the picture, the story felt very thick and bogged down by years and years of resentment and humiliation and sorrow and, underneath it all, an earnest desire to forgive and move on. You felt the older sister's resentment at being prematurely thrust into the mother role and then all at once shoved out of it. You felt Joey's desire to believe in her father even when it looked like that would have been a mistake. You felt the pressure under which the dad constantly labored. Most of the stories and relationships were like that. Underneath the clever comebacks and complicated analysis, there were years and years of development and emotion.
Then, all at once, Joey and Pacey broke up for a reason that had only simmered for a month or so and the show sort of took off at breakneck speed. I found that to be problematic. I get that the characters were meeting new people and doing new things, but I felt like the core relationships and the insecurities and experiences that had made the characters feel so weighty in the earlier seasons all suffered during the college years to the extent that it didn't even quite feel like the same show.