I hate the art, but beyond that I don't think it's that bad. I wish people would just ignore it instead of giving it negative attention.
I dislike what the show represents more than the show itself. Hell, I dislike what the original Thundercats represented, too. Obviously selling toys is an important part of animated shows, but that doesn't mean they should be such transparent toy commercials.
I feel like stuff like this underestimates kids' intelligence. Stuff doesn't have to be stupid and ugly in order for kids to enjoy it and buy toys of it. As much as I loathe MLP:FiM's adult fanbase, it's a really good example of a show caring more about being interesting than selling toys (despite to that being its purpose.) Same goes for the new DuckTales. You can tell the people working on these shows really wanted to make something enriching and clever for kids to watch. I don't sense the same amount of dedication when it comes to all the reboots on Cartoon Network.
The autistic hatred for TTG in particular has gotten out of hand. I think the writing of the show has improved, and I think the inclusion of other DC characters was an interesting choice. Frankly I'm just glad this only happened to Teen Titans and not something I actually care about, like Young Avengers. Thank Christ I don't live in the "Young Avengers Go" timeline.