There must be security camera footage along the street before and after the car's location. It doesn't seem implausible to find the damaged car leaving that wasn't damaged coming. You could also look at the damaged vehicle to figure out the paint of the other car, I'm guessing something would be left behind. You could contact repair shops in the area looking for a match.

I don't know - I'm not a cop but there are certainly many possible avenues of investigation if people were willing to try.

Sure if you have infinite resources to throw at a problem, you can do a lot. The actual question is: how much effort is all that, is it worth it, and what's the chance of success?

Realistically, for a property damage case, you're not going to get ten cops scanning hours of grainy security camera footage (that may not exist) from different angles and running all over town for weeks checking every auto body shop in the city looking for paint matches. Even if they did that, there's a good chance they'd fail (e.g. no video, no legible shot of the plates, culprit doesn't take his care into a shop), so they're not going to try.

Investigating would require some resources, yes though obviously not "infinite" resources. That's why we fund police departments, hire investigators and officers, and give them authority to conduct investigations though.

Ignoring, and tacitly permitting, crime results in more crime which in turn results in greater demand for effort. Thoroughly investigating and resolving crime may be more expensive than ignoring crime in the short term, but long term it pays off.

Yeah it was a hit and run at 3am. Do you watch your car at all times?