I think there's a bit too much focus on the relationship between building heights and density, in that density implies "skyscrapers." But in the more residential areas of Philly not filled with blight and abandoned buildings, there's a decent amount of density despite the fact that much of it was constructed with a 35' height limit. But it was also constructed without any setbacks and with very little off street parking taking up space.
Personally I'm fine with taller buildings, and there are definitely places (near transit) where there should be taller buildings, but you can pack quite a few people in without them.
And the point of packing people in is that if you do you create walkable neighborhoods with sufficient demand for a variety of local retail.
