The Google Image search isn't reflective of an actual car factory.. There are of course hundreds of workers there but final assembly facilities produce something like 1 car/minute. They're heavily reliant on robots - most of the parts move around the floor on autonomous transports, the stamping is all robotic, all of the frame welding is robotic, paint is of course robotic.
GM is of course tied in with the UAW, so they're going to be as favorable to labor as possible in their promo videos, but take a look at this video of one of their production facilities, this is reflective of the amount of manual input into modern automotive production: