The age gape issue with Shuri and Namor isn't the first time I've noticed people lean into racism and racial stereotypes to inaccurately calculate a character's age.
On the Get Down fans assumed Shaolin Fantastic wasn't a teenager like the other characters before an official age was even confirmed. Antis were harrassing people who shipped Shaolin and Zeke, a confirmed 17 year old. They saw a dark skinned young man, obviously pretending to be grown, ignoring every narrative que that painted the two as equals. Even after the age and the romantic attraction (though unrequited) was confirmed the age gape controversy didn't die down.
The racial stereotype is not the over sexualized and adult black male, but the sexless black woman. Her thin frame does make her great for casting as teenage characters, but it didn't serve her in this movie. There are ways they could have aged up her appearance through make up, wardrobe, or editing but even I forgot about the 5 year time skip from the Blip. So I can't really fault people for not remembering if they skipped the after credit scene. However when you compare Shuri's age along the entire Marvel MCU timeline she can't be a minor anymore. Instead of Antis letting that go, even when the evidance is right in front of them, they continue to act as if Shuri is still a teenager. At this point people need to unpack their racial biases or accept that they can't due basic math because Tousaint is obviously 5-6 years old.
[Shuri's age BP] + [Tousaint's age BPWF] > 18
Even if you don't count the Blip since she was snapped, Shuri is still an adult in Wakanda Forever.