Even this late in the season?
Yes. Crabgrass can germinate again in the summer plus a bunch of other stuff. And you will be better served if you get a jump on pre-em going into next season, meaning when you put down pre-emergent in February (the time when it should first be put down), you don't have a lot of winter broadleaf and residual from this summer
And just note that you shouldn't consider Celsius or another post-emergent herbicide the easy way out (ie in lieu of hand pulling). Unless you're pulling every weed by it's root system
, you're actually helping most weeds propagate by hand pulling. Hand pulling is good weeding practice if you can get the entire root system and because it can make room for the turf grass to thicken up and prevent future weed growth (thick grass is always the best preventer). But I'm your situation you have no thick grass so herbicide is not just a luxury but a necessity in my opinion if your goal is to reduce weeds in the lawn during your first year, which is what I recommend.