If Republicans ever begin to win African Americans again, on a large scale or at least 55% of them, DC would become competitive.
This. DC is comprised of Less-affluent African-Americans, African-American Government Employees, White Government Employees, and White Liberals. If any of those groups suddenly jumps to the GOP coalition, DC becomes competitive. See 1994 D.C. Mayoral Election.
A 56-42 loss is hardly "competitive".
Competitive as far as DC as concerned, especially as some people in this thread are like "zomg DC will always go 75%+ Dem forever".
Now, Schwartz getting to 50% in that election may have been a much steeper climb. A third party black candidate may have been able to split the vote, but there's a risk such a candidate would attract a lot of protest votes that were going to Schwartz.
I don't really think "competitive as far as DC is concerned" really makes sense. Either something is competitive - either side can win - or it isn't. "Competitive as far as DC is concerned" still means it's not close to winnable for the Republicans and therefore isn't competitive.