Look, the jams are real, nobody will lie to you about that, but they are not some eternal gridlock that swallows your whole day. Avoid the main ring roads at peak morning and evening hours and you cut out most of the pain right there. The centre is walkable and the metro covers the rest, a car is really handy when you need to hit the outskirts or haul shopping back to your place. To find a car to rent in Moscow just browse the listings this site
https://getrentacar.com/en-US/russia/moscow .