This is grandstanding by the Democrats, because the Republican controlled Senate will never take it up, because a state of DC would mean two more Democratic senators, making it much more difficult for the Republicans to win control of the Senate in future elections.
Nevertheless, it's a very interesting signal, as it is the first time DC statehood has ever gotten a vote, and it raises the prospect of the Democrats moving forward seriously with this if they retain the House and retake the Senate and White House this November.
They would face a GOP filibuster in the Senate, which would reveal just how serious the Democrats are, because the filibuster could be defeated, but likely not without great effort.
The question of whether statehood is the right thing to do because everyone deserves equal representation is not a straightforward question. DC residents have never had full representation, yet people continue to live their voluntarily; they are not imprisoned, and can move out. So lack of representation has not been forced on them.
In addition, they could be given full equal representation by returning the residential parts of DC to Maryland in a process called retrocession (as the western part of DC, although undeveloped at the time, was previously returned to Virginia, which is why DC is not a perfect diamond, but follows the Potomac River for its western border).
Retrocession would be more amenable to Republicans because it would give the residents political equality without tilting the Senate more toward the Democrats, but it is not supported either by Maryland or DC residents. My reading of Article IV section 3 (creation of states) suggests this could be forced on Maryland without its consent, but politically that's not likely to happen.
The Constitution (Article I, section 8), requires that the seat of government be separate from any state, but does not specify that it has to be a city. So the capitol hill section of DC could be legislatively excised from the rest of the city in making DC a state, and leaving it as federal territory. I suppose a constitutional argument could be made against having that federal territory be wholly contained within the new state. But if the national mall was (appropriately) kept within the federal territory, and the tidal basin, that would make the southern part of the federal district border on Virginia, making it mostly, but not wholly, encircled by the new state.
This is an interesting political question, and it would be a notable historic event with notable political consequences if it happens, but it's not hugely important in the big scheme. As noted above, DC residents have volunteered to not have full representation; they're not repressed. Republicans would have a harder time winning the Senate, but with Colorado and Virginia having gone blue, North Carolina and Texas trending in that direction, and the GOP base of older white people declining as a portion of the population, the party is going to have to reinvent itself over the next generation to avoid a long period of irrelevance anyway.