It feels like different systems are better and worse at that. On my 2019 Honda Insight, it's actually pretty smooth and does a good job of staying in the center

It feels like different systems are better and worse at that. On my 2019 Honda Insight, it's actually pretty smooth and does a good job of staying in the center of the lane, but it won't turn the wheel too much -- if you're taking all but the gentlest curves, you're going to be turning the wheel. On my mom's 2018 Subaru Outback, it's exactly what you're describing -- it's fine in a straight line, but it doesn't really seem to judge the curve of the lanes as much as simulate a pinball. (I don't think I ever tried to let it take a turn on its own!) I've only ridden in Teslas, not driven one, but it seems like it's probably got the best following/lane-keep system on the market, although the last time I rode in one -- admittedly about two years ago -- it was markedly jankier when the driver engaged more "self-driving" features, e.g., have it change lanes, take exits based on its own GPS guidance, etc. It was impressive that it could do it, to be sure, but it was the self-driving version of your reckless friend in high school you do your best never to ride with.