I disabled watch history, which appears to disable most personalization features, and my suggested videos are mostly sensible. (This disables the "Home" page entirely, but the chronological Subscriptions feed is still fully functional)

i.e. the suggested videos in the sidebar will always be relevant to what I'm currently watching, whatever that is, rather than stuff youtube thinks I might like in general.

I know it's doing something good because youtube keeps nagging me to turn watch history back on again.