The GoTG and Black Panther are vastly different in tones
, You know what isn't as vastly different in tones Man of Steel, Suicide Squad, BatmanV Superman, Wonder Woman, ZS Justice League, Harley Quinn but know what DC movies general get complained about by some fans Shazam, Aquaman and WW84 aka the movie that shift away from "the DCEU overly serious tone". You can't take similarness or variety complaints too seriously because if it was real thing they would be complaints about DCEU as well.
The complaining is really about not liking a MCU style of humor, it is lazy complaint imo to call them all the same similar. Note it is not some big insult to say that they are similar because they are things that are suppose to be similar. One ,they are in the same universe so MCU has overall universal tone(just like DCEU) that all its movies and shows have, yeah they are suppose to feel and look alike. Two, a vast majority of the MCU movies so far are Origin or Introduction stories which there is a general similarness in those type of stories I mean Iron Man and Dr. Strange is basically the same story. I am going to talk about last component in a second but if you notice in all of chances to talk about this stuff. It is humor the only thing that pops up when people complain.
Anyways the last part is what MCU story or character is suppose to be different in presentation and tone? Iron Man, Peter Quil, Antman and Spiderman are quippers, Dr. Strange and Captain Marvel are sarcastic both of those things lend themselves to be presented in comedic moments. Thor, Black Panther and Captain America are more serious and their movies in general are more serious than others.In the MCU with maybe exception of Thor Ragnarok , the MCU has present stories and characters in manner they should. And this big point the MCU heroes they have used so far are generally the same style of heroes and even in the comics they aren't much variance. If the MCU was using Hulk, Blade, Wolverine, Punisher, Daredevil, etc or telling some darker or tragic story they would be a expectation for some vastly different tone.
Now I wish people would just be straight forward in just saying they don't like the style of humor but quick easy lazy complaint to say they are same or manufactured. GotG and Antman are comedies, They have big comedic set pieces which are just as important as the action set pieces. Captain America, Thor and Black Panther are straight up action/drama but they have occasional joke usually coming from a comedic relief character in Thor it was Kat Denning Character, in Black Panther it was Shuri. Black Panther doesn't not feel a like GoTG or Antman.