I didn't look for implied racism in your statements, if you that is what you are suggesting. My reply was more to the point that this 'race card' description is used to trivialize discussions of race, its history and legacy, far too much in our society.
I don't think Mayweather exhibits any of the typical stereotypes ascribed to blacks, or black male characters, that litter some Hollywood productions, which is a good thing on the part of the ENT writers. They even removed him from the asexual category, with Gannett Brooks and the implied Mirror Universe-relationship with Empress Sato.
My concern with Mayweather, and other characters of color, is more of a tokenism issue. They are sort of there just for background, for symbolic diversity, and the writers don't seem to invest enough in the characters to make them interesting, to make the audience want to see more. For me, I think there is a racial/cultural component to that.
And it is vexing, especially with Mayweather, because the writers seemed to start him at an interesting place. As a Boomer he had outside knowledge/hard bitten experience about a lot of species that Archer and company rarely if ever relied on or consulted him about, since T'Pol and her Vulcan database were used as a go-to. Perhaps its just me but it seemed like Broken Bow was setting up a Travis-Trip friendship that went nowhere. There was also some interesting Archer-Travis interplay in a couple episodes that went nowhere. And that left field mention of Travis by Hoshi when she was thinking about the people she would miss, while with that psychic alien in the Expanse, and that went nowhere. (Would it have hurt them to have a Travis-Hoshi relationship, or a Travis-Hoshi-Malcolm triangle? It would've given all three of them something more to do). And in TATV, they didn't even change his rank (like with others), which reinforced that B&B had little idea of where they wanted to take this character (and many of the other characters as well).
As I said before, I can understand why Nichelle Nichols and George Takei didn't get much development on TOS, though they were given some hobbies which was better than nothing. I do think race played a part in their development or lack thereof. Even when creating Sulu, the writers said he would be inscrutable to other Asians (why? Because Asians were inscrutable to them perhaps?) and that he would consider himself a French swordsman/Musketeer type (why? Once again, something more familiar to them; something Eurocentric).
With Geordi, it made little sense to me, why they didn't capitalize on LeVar Burton's fame, as I've written before. Though he was promoted and contributed to the ship quite a bit, his character didn't change much at all. There was no arc for him. And even in NEM, despite the well established friendship between him and Data, LaForge isn't even allowed to give the android's eulogy. Crusher didn't get much development either. Sure she switched jobs a couple times, admitted-under duress of a sort-her feelings for Picard-but there was no growth for her. It's not like she started the show hating Picard and then learning to respect and love him or something like that. She had largely forgiven him when TNG started and the writers were reluctant to explore the one aspect that could show change for her character, or if nothing else, a change for Picard from stuffy bachelor to family man.
DS9 is the anomaly. It wasn't perfect, but it got it closer to right than the others. Sisko came across as relatively three-dimensional. They dropped the ball with Jake and some of the writers even mentioned that they did so in the final season.
With VOY, others have long pointed out how Kim and Chakotay were shafted. This is juxtaposed with Janeway's development and the rise of Seven of Nine (but how much of that was based on her sex appeal as opposed to Ryan's solid acting?). But overall, I think Mayweather fared worse than most of these characters, due in part because he was developed after all of them, in the 21st century, yet his lack of development feels like he was created as part of daring sci-fi program from the 1950s, where it would've created a stir just to cast a black person in such a high-profile (relatively speaking) role.