This fits my observations. It seems to be easier for some very small, tight-knit communities. I can see why migration would be more feasible for those.
The larger trend will probably be much slower. Lemmy and other solutions need to grow, develop, and do some search optimization. I suspect that the number of mods on Reddit will slowly go down over the next year or two. Hopefully, most will find a new landing place.
Yes, “people of color” is considered respectful.
And you’re right, language can change pretty fast. I’ve seen plenty of respectful words become slurs. I’ve even seen slurs be reclaimed by communities. Don’t even get me started on person-first vs identity-first language.