My experience with a road trip rental of a 2020 RAV4 is exactly the same as what you describe.

The ACC was great, and very useful in both high-speed traffic and stop-and-go traffic.

But the lane-center tech was useless, regardless of the road conditions. Even with full sunlight and freshly-painted lines, it didn't work reliably.

When I was test driving a RAV4, the dealer told me not to use the lane-centering when in the slow lane, allegedly because people are coming and going a lot. But it was clear that the real problem was that it would keep you centered even as the line on the right veered off for an exit, which would drive you right into an overpass.