Well if someone disregards a cartoon in such a fashion that's their own problem, I say. But I don't think it's so bad as long as you recognize it's nostalgia that draws you in. Ten years from now there will be college students remembering today's cartoons fondly. Cartoons, in essence, are supposed to be fun to watch. If age enhances the fun factor, so be it.
As for these cartoons themselves, I really think they're definitely not the worst ever made.
Transformers: Having the DVDs, I still enjoy them. Yes, that's nostalgia talking. No, it's not a great cartoon. But it is just fun to watch.
Silverhawks: Never saw it in its initial run. Watching reruns on IN2TV, it's fun to watch because of how ridiculous it is.
Pokemon: Nostalgia lets me get through the first season without screaming. Beyond that, yes, it does get very tedious. I find it almost painful to watch now.
13 Ghosts of Scooby Doo: I never liked Scooby as it is. 13 Ghosts was another spinoff that I avoided. But there are worse spinoffs out there.
Jem: Also never saw this one. It's funny because of how outdated it is, not terrible.
Goof Troop: Not Disney's best, but not their worst either. Fun to watch in small doses.
Captain Planet: This cartoon actually played a major role in building my political position. Still love it to this day, but also fun to laugh at the ridiculous parts (I could never figure out, as a child, Dr. Blight's problem. All the other villains had something to gain out of destroying the planet, be it money or thriving off of the pollution. But Blight was just evil with no real reason.)
Everyone has their varying opinions, of course. They may age well for some, but not for others. I always looks for an episode of a cartoon online before buying the DVD, just to make sure I can still enjoy it.