Hispanics and white males are the majority of the fan base for MLB. African Americans have been in decline since the 90's or late 80's in terms of fandom for MLB. The weirdest part is that MLB had some of the greatest African American athletes in the 90's not named Michael Jordan or Bo Jackson with Griffey, Henderson and Thomas. After Bo Jackson and Michael Jordan the biggest poster sales were Griffey and Thomas. Back in the 90's jersey sales were not all that available I don't even think MLB marketed or even sold jersey's in the 90's.
The popularity in culture especially in African American culture during the 90's and into the 2000's were jersey's along with shoes. MLB tried to cut into the action with the shoes but by that time Jordan was just dominating everything. MLB missed out on the jersey sales in the 90's that made the NBA popular. Also baseball in the 90's by the youth was thought of as a non athletic game. Though during that time you had some of the most athletic players in Bonds, Griffey and Henderson that the sport had seen in a long time.
MLB did a poor job in the 90's of promoting their players and by the time the sport turned the corner and started promoting Griffey it was far to late. Jordan and basketball took over MLB in the 90's and then with the FOX deal for the NFL went through that started to put the nail in the coffin for MLB in terms of ruling in popularity. MLB has gotten better at promoting their star players but is still far behind the NBA and NFL and is just ahead of the NHL which also has a problem promoting its stars.
The next biggest problem is the don't stare at home runs crowd and don't celebrate at all unless it is for the team I cheer for otherwise it is against the game of baseball. These unwritten rules need to be abandoned if the league wants to grow with the youth. Younger people love Ohtani, Harper, Trout, Tatis and Vlad because they bring an excitement to the game. They will flip their bat when they hit a home run and celebrate. The Cardinals way of baseball needs to die and die fast if MLB wants to expand and keep on being a relevant sport.