The problem is that this rating system is wrong.
The Simpsons quality was entirely related to who was in the writer's room overall, who was writing individual episodes, and who was directing.
Season 1, almost every episode is a formative, proper sitcom episode. This is because James L Brooks had a certain set of "rules" everyone had to follow.
Season 2-3 are actually the best Simpsons, where the showrunners were writers who knew the rules but were able to develop everything, and do new storylines.
Season 4 is still good, but the showrunners admit that burnout started to happen for the original crew. Al Jean and Mike Reiss left to do "The Critic" after this.
Then 5-7 the show is at its most widespread and mainstream, but also has randomly bad episodes because almost all the original writers were gone. The showrunner for Season 5 was David Mirkin, who was way, way more "cartoony" and "tongue-in-cheek" compared to what Groening was trying to do, which was more based in reality.
After that, Josh Weinstein was in charge, and man this guy...He just seems to be the most marged guy in terms of episodes in the "classic era". I really don't like what Simpsons became between Mirkin and then Weinstein, because that was when flanderization and insane plot nonsense started to become accepted as what the Simpsons was. The scenarios started to become unhinged.
By the time 1998/1999 rolls around Groening is more invested in Futurama, so Simpsons just sort of falls into oblivion, and instead we get 5 solid seasons of Futurama episodes with stupid environmentalist messages every now and then.
What's really interesting though is how certain Futurama writers like David X Cohen and Ken Keeler who made great Futurama episodes also made some pretty cringe Simpsons episodes. As in, Simpsons and Futurama do not have the same kind of humor or storytelling.
It's also important to note that good episodes from mid or bad seasons like "Radioactive Man" or "Homer's Enemy" are usually written by someone that usually writes good Simpsons episodes, case in point John Schwartzwelder.
But ultimately, the fact is that even guys like Weinstein who I don't think were well suited for the job, still made good episodes (Who Shot Mr. Burns?). But, After a certain amount of seasons and episodes written, it doesn't matter who you are. Al Jean, Mike Reiss, James L Brooks. You can't make "Season 28" of something GREAT like Season 1 or 2, its impossible. You've already done it all and back. How many more people are going to date marge's sisters. How many naughty things can Bart do before you start repeating? How many times are the Simpsons going to become famous? Eventually it just becomes "plug topical thing into Simpsons" which is not really the original spirit of the show, which was a bunch of Harvard Lampoon guys reminiscing about family life from the 1950s-70s. The same rule of "what the fuck do we do now?" applies to South Park, Family Guy, any of these shows that just keep going on no matter how bad it gets.
TL;DR To me, "Krusty Gets Busted" is worth more than the last 20 years of Simpsons episodes.
