Sorry Bob, but you are way off on this one. First of all, your references to older episodes were all from season 1. That is a poor choice. Those do not hold up well. The golden years are season 2 through 7, 8, 9 or 10 (depending on personal choice). The reason for the greatness of those seasons, especially 2 through about 7, was the writers and producers. Conan O'Brien in season 4 and part of 5 (who of course left for his own show). Al Jean and Mike Reiss left for the Critic (although Jean did return). David X. Cohen left for Futurama. Plus many, many more (often leaving to work with the people I mentioned). Then some really poor show runners, and the Simpsons did go downhill. I still watch those episodes and laugh out loud. I also am amazed at how clever they were. That is no longer true, and it has nothing to do with nostalgia.
The only correlation in tv I can make is MASH. The first 5 seasons were great. Yet Larry Gelbart left after season 4 (he did still consult but was no longer involved in day to day stuff) and Gene Reynolds after season 5. From that point on the show went down hill, just like the Simpsons. The brand is still there, but the people that truly made it great had moved on.
Of course turnover is not always bad. In fact, the Simpsons lost a ton of people after season 3. Yet the group that replaced them brought about what I consider the best season, season 4. 4-6 are simply genius, and there are only a handful of mediocre episodes. Yet the majority of those guys are gone from the show.