For DC itself I agree.Resizing DC making it smaller and making a new state for the tax paying citizens of the old DC area is not.
DC,Puerto Rico,Guam,American Sāmoa,and the U.S. Virgin Islands would all be solid blue states giving Democrats 10 new Democrat Senators,a few House Reps and EC votes. Mariana Islands would likely be a swing state.
The 23rd Amendment grants 3 Electoral Votes to DC. In your scenario of making the residential area of DC a state, an amendment would be needed to remove the 3 Electoral Votes granted to DC as the few hundred people left in DC would wield too much power in The Electoral College.
The 23rd Amendment does not grant exactly 3 Electoral Votes to DC The amendment grants to the district electors in the Electoral College, as though it were a state, though the district can never have more electors than the least-populous state. How the electors are appointed is to be determined by Congress.
And here, you reveal the real reason that you are advocating for statehood. If it were just about representation, it could be ceded back to Maryland and those folks would be Maryland residents. This is the proper way and also has a precedent in that land was ceded back to Virginia in the past. However, I rather think that we just leave DC the way it is.