There are other issues as well, such as the fact that DC is a city with a very small land area. The land of the District of Columbia was contributed by the state of Maryland.
The state of Virginia had also contributed land to form the District of Columbia. But that land was eventually given back to Virginia. Statehood rights, voting rights, etc could be achieved by giving back the remaining area of the District of Columbia to Maryland.
The fact that the area is small does not make it any more fair that 700,000 people have no right to say how their federal tax money is spent. Why should Vermont and Wyoming with less population have this right? DC sends 4 times as much money to the feds than it gets back in services. Far more than any state’s percentage.
In general it appears that DC residents don’t want to be a part of Maryland, and most in Maryland don’t want DC, especially the political class. Interesting fact, Virginia’s piece was given back because DC was eliminating the slave market because of reaction of embassies in DC. The folks in Alexandria wanted to keep their slave market so pressured to be detached from DC. DC should get this chunk back and then would have the population of probably 7 or 8 states. Virginia would be more likely to be solidly Republican in that case, so DC’s solid Democrat base would be offset by Republican Virginia. Of course, the politicians would never go for that either. Whatever happened to “taxation without representation” which we fought the British over. Does DC need to rebel to be equal to all other US citizens? Should they put 3/5ths of their federal taxes in escrow until they have these rights? DC can vote for President and Vice President, but lacks a Representative and 2 Senators.