D.C. congressional representation was a possibility last decade, in part because of a proposed compromise that pleased Republicans: we increase the chamber from 435 seats to 437; D.C. would get one seat, and overwhelmingly Republican Utah would get another.
Now this wasn't just arbitrary, and Utah wasn't chosen just for being the most Republican state in the country. Utah spent last decade as the “First Loser” in the reapportionment lottery. The state just barely missed out on getting a fourth seat. Put another way, a fourth Utah seat was the 436th seat according to the reapportionment formula.
But Democrats blew up statehood over gun rights last Congress. Then Republicans took over the House. D.C. representation was basically dead for now, and the reapportionment makes it even more dead.
Utah got its fourth seat. The 436th seat this decade is North Carolina — it just missed out on gaining a seat. Who knows if that seat would have been a Republican or Democratic seat? But we know this: it's not a good counterweight to a 100% liberal Democratic D.C. seat; and it's nothing like a 4th seat in Utah, the most Republican state in the country.
In short, Democrats can no longer buy off Republicans for DC representation by adding an extra seat in the other 50 states.