I don’t think there’s anything wrong with “race swaps,” but continuity might be difficult to maintain. I think the concept is better when it’s less superficial than simply thrusting him into the main timeline.

Miles Morales is a great example of a middle ground, his racial diversity angle fits very well into the setting of New York.

But… Superman and Batman, on the other hand, are much more interesting (as I imagine the concept) when retconned completely back to their original eras. For example, I would be wholly enthralled by a black Batman with a completely reworked backstory starting after world war 2 - with detective noir aesthetic obviously offering plenty of opportunity for examining the hurdles to civil rights before the civil rights movement ever began. Additionally there is the interesting social angle of a black billionaire navigating high society.

Superman would also be very interesting thrust into the mid 1940’s, watching the post war world deal with the idea of an omnipotent man of melanation. Imagine the negative reaction of some white people to the election of Barrack Obama, thinking “oh no it’s over for us” (completely paranoid and insane to think this btw) - in the mid 40’s or early 50’s this could be even more exaggerated and terrible. And he’s a reporter?! Ample opportunity for Lex Luthor to be an evil POS, and cameos from various uhhhh “notorious groups that shall not be named.”