I agree that the ratings are wrong for certain drivers but, regarding Yuki, he started off the season quite well and then he's absolute toilet at Red Bull. However, does that make him a bad driver now?
Like, if you took him out of Red Bull in real-life and into, say, the Aston (or even back to VCARB) then would he be as bad? I don't think so. So, while he shouldn't be winning races, it's not especially because he's a bad driver. So he doesn't particularly need dropping too much himself.
So is it the Red Bull? Well, if you nerf the Red Bull so Yuki does terribly in that car then Max also won't be winning races anymore, which doesn't reflect reality. So you could bump Max's rating up to counteract the Red Bull deficit... but what if he moves to another team? A Super-Max would win every race as his stats have been balanced against the Red Bull and you stick him in a McLaren and he's lapping the field. And he's good, but he's not that good.
There's probably a fine-tuning balance that needs doing. It's probably not as simple as having all drivers have a particular performance in each car. There's like 50 drivers and 13 cars. (the MyTeam, APXGP and Konnersport cars additionally to the real-life 10) and (15 if you count the three MyTeam starting levels as its own car performance). That's already like 700 different permutations of driver-car relatability and ideally you want to minimise variables in things.
I'm probably overthinking it. The driver update should come out soon enough and the car performance a few weeks after that, i'd say.