It was really more than just recycled gags and dialog. Almost all Rita and Runt, Chicken Boo and Katie Ka-Boom cartoons are the exact same thing over and over again. And as great as Pinky and the Brain usually were, their cartoons were the textbook example of cartoons that repeated the same formula all the time.
It was always a crapshoot going into Animaniacs. Which characters would we encounter today? But usually once once we discovered which characters we were getting we were usually offered nothing new. Again this is especially true of Rita and Runt, Katie Ka-Boom, Chicken Boo and Pinky and the Brain. Even though Tiny Toons used the same integrated cast of characters the storylines more than made up for it.
Additionally, Tiny Toons got better as time went on. Animaniacs just got worse and worse. I enjoy the best of Animaniacs but I think as time goes on the show is very slowly going to fall out of favor as more and more people start to see it's faults.
The problem with this show is that (with only a few later exceptions) only the first dozen or so episodes were animated in Japan, which was much different than Ducktales, which used TMS far more in the first season. This meant that the majority of the Rescue Rangers episodes feature bland and sometimes absolutely horrible animation. So unless you really enjoyed the characters, the sped-up voices and the repetitive stock music, the show didn't have much repeat appeal.
Talespin, on the other hand, had likable characters, intelligent plots, fantastic music, a really well thought out premise and universe and usually very strong animation. It holds up very well today.