Something interesting to me, as someone with a 2020 base-level Forester, is that you describe my experience completely. It works great on most highways, but needs me when lanes split or merge.

Of course it's not 1:1. AP has other features, such as a much nicer UI that better reports what it thinks it sees, and I think has sexy lane changing features and such.

But it makes me feel that FSD was more business necessary to keep a competitive advantage against cheap cars. Soon many cheap cars will have AP-like features at comparable fidelities.