If I were honest, I'd say I don't know the Thundercats too well, except watching a few episodes with my sister years ago. Even still, some scenes stick out to me. Plus I do think the series is awesome. However, I do not like the reboot coming out.
1, it's more Hollywood rebooting of old properties, but that not so bad. 2, the animation is a chibi, reductionist style that reduces the characters to their most comical features, which I'm not into for reasons I'll get more in-depth about later.
One of my major gripes with the show are the showrunners. They're the types people abuzz about Roar would call Soyboys or Cucks or SJWs. They're right, sort of. It's more I don't know the showrunners' politics well, but it has more to do with what they seem to be doing with the characters. The designs are reductionist, but also altered, such as the design differences between Cheetara and Lion-o. Lion-o seems purposefully designed to be less leader material than before and the way he speaks sucks! For example, he calls his sword a "magic slicing stick" like a child would and seems more generically excited, such as when he recoils at the fact we might not know what a Thundercat is. Cheetara looks like a butch lesbian with no boobs and more of her natural feminine features de-emphasized because being a woman is a crime in the current year. The design of the younger children is made to be more gender neutral rather than the viewer being able to tell them apart.
About the comical features, this show wants to throw away the dramatic elements of both the original and 2011 version of the Thundercats and has done so. All you're left with is the absurd, silly-billy ideas that Thundercats seem to wear on the outside, without the serious depth and stakes and character on the inside. The comparison between Roar and Steven Universe is the art style, but the comparison between Roar and Teen Titans GO is the fact that these once-emotionally captivation and complex characters have been reduced to nothing but a joke, and is easily seen in this trailer. To me, the latter is the much worse crime, because even if you're not into the SJW aspects of Steven Universe, their characters aren't jokes or shallow, they're emotionally in-depth.
It's a crying shame to see something that was twice explored as much as possible, be turned into yet another ADHD-riddled, loud, in-your-face, obnoxious mess.