Citation absolutely needed. Show me source of your numbers. Brooklyn runs the gamut from skyscrapers to single-family houses, but the average construction is 1-3 story apartment buildings, just like the mission.
In any case, even if you're right, it's not a counterargument: how does the western 3/4ths of SF compare to Brooklyn? Why should we be focusing on the Mission, and not, say, Sea Cliff?
Let's try to put a condo building to Jack Dorsey's mansion and see what happens.
You're comparing SF in 2008 to Brooklyn in 2017. Click the source link, and you'll see that current estimate for the Mission (30,408/mi^2) is much closer to that of Brooklyn. The difference is only ~20%.
Not so dense by the standard of Brooklyn, either. Brooklyn is 1.5x denser than Mission.
And that is the average density for all of Brooklyn, Brooklyn being 40x larger than the Mission District.