I think we would've won more black votes if Trump held any events at black churches or held rallies in black areas. But he didn't visit any black churches that I know of. Would've loved to see him visit Detroit, or a rural black county in Georgia even if just once. He didn't do that so far as I know. He focused his rallies mainly in blue collar majority white areas, which played to his strengths. Though I think with a few well placed events he could've gotten a few extra percent of the black vote. Maybe not enough to justify it.

The Platinum Plan was so over the top unrealistic that everyone knew it would never happen. I'm not sure how much was spent on ads targeting blacks or urban demographics, though Kim Klacic and Billy Prempeh mentioned that the RNC was hesitant to spend any money in cities.

Hispanics are a more promising voting block as you mentioned. Especially since Dems are throwing them under the bus.