The other side of the equation is that rhetoric also needs to clearly encompass the white working classes.In other words, "Sorry, minorities. Maybe next generation." Do you think they've heard that tune before?
Here in the UK, studies have suggested the minute you launch into discussion of things like "privilege", you've just made it a ton harder to get through to poor white (and moreso probably male) kids, because they hear that and they start to think this is just them kicked to the back of queue again. Never mind that many of them are heavily disadvantaged and inclined to resent arguments that they have privilege (even if it is technically true).
In a sense, there is limited public attention out there, and if a candidate spends their time routinely checking minority tickboxes, that's less time they are going to spend ticking other boxes. BLM is huge, front page stuff, whilst whole post-industrial communities struggle and die with far less notice. So when Trump stands up and says "I'm for you guys!", it doesn't so much matter whether it's really true but that someone is clearly putting them up front and centre, and they like it.
Whether the Democrats like or not, they have conspicuously delivered enough that these people want, and they aren't really communicating with them in a way that makes them feel and special and loved, either. So they turned to Trump, who at least did the latter.