Please don't speak as though you speak for all fans. I was much happier with S1 of PIC than I was with S3. I understood what the premise would be and I was not clamoring to see the return of the entire ensemble. Doing so felt like TPTB admitting that the show was a fundamental failure, and I found it pretty disrespectful to the original cast of the series (barring the ones who were retained).
Frankly, I also find S3's message of, "once you become of a certain age, nostalgia is really all you have to look forward to" both unrealistic and somewhat disrespectful to older people. The show could have tried to send a message that just because one of the biggest adventures of your life is over doesn't mean you can't have more amazing adventures with new and different people, but instead it essentially went for the lowest common denominator and took the easy way out.