They are pushing enough cars, I think. One factory producing about 4000 cars per week is a very large factory, indeed!

I think Tesla is continually thinking of ways to improve the design, develop new techniques that can be automated easier. And I don't think these are all making it into the Model 3. Some will need to wait until the Model Y or even later. For instance, apparently the Model Y will ditch the 12 volt battery and feature a MUCH shorter/simpler wiring harness (which is one thing that's incredibly hard to automate, so making it simpler should help a lot): https://insideevs.com/tesla-model-y-ditch-12-volt-battery-95...

(with the caveat that Model Y plans seem to change each quarter)