Nothing wrong with reboots long as they respect the source material. Brands like Batman, Spiderman, Scooby Doo, Transformers, Ninja Turtles and Power Rangers perpetually change and make themselves different than before, and that's part of their longevity. Taking strong, iconic ideas and reiterating on them can lead to bad results sometimes, and sometimes it can lead to definitive best versions… and if a franchise goes through three or four relaunches over decades something truly good can eventually come of it. (Though its easy to get fatigue if you personally have followed a lot of those iterations and just see repetition after a while.)
We wouldn't have Batman TAS if not for 60's Adam West Batman and Superfriends and the Tim Burton movies. We wouldn't have Scooby Doo Mysteries Inc without countless Scooby shows and Movies. Spectacular Spiderman is probably the best Spidey is going to be. The Turtles 2003 is fantastic, but the CGI show was okay.
But you have to respect the source material, which both thundercats Roar has failed to do. The 2011 show took it too seriously and had no fun with it, and Thundercats Roar is a complete abomination. Thundercats might be a concept too ingrained int he 80's to really truly work anywhere else, same as He-Man... at least until we're far enough removed from those versions the bad parts can just be completely ignored instead of faithfully kept on no matter how dumb. (I'm looking at you, Mecha-neck.)
That said, I don't know what you do with Rugrats that they didn't already do in a 10 year stint without just changing it entirely.