Don't confuse perfection with intention.
America is not perfect, but ever since the Declaration of Independence was signed America has moved toward achieving what was clearly an "aspirational" goal of equality.
MLK's vision of America speech is an echo of that original goal. Making America Great Again was about returning to that dream at a time progressive liberals were promoting a new dream... one based on "equity" over equality.
Progressive liberals embrace the idea that the majority has a right to impose its will on the minority rather than the majority working to promote equal opportunity for the minority.
As this country becomes more diverse (my family includes Africans, Asians, historically European and Hispanic members), we see a new form of oppression arising where the majority feels free to impose mandates, censorship, and laws on those that disagree with them.
I am not a fan of Trump the man, but I do think this country needs to return to the vision of the founders, echoed by MLK, where we operate as a one nation and not a collection of identity groups forming coalitions to oppress other identity groups using the government to do so.
What scares me about progressive liberals is their willingness to use government to coerce behavior rather than use government to protect individual freedom. In a way, Democrats are returning to a form of societal slavery and that is something we should turn away from...