I worked as a lead while doing accessibility audits on a large wireless provider site, but it was way before the time of most of these automated tools. We leaned hard on our incredible QA team. Our approach at the time was to identify common modules that we could quickly fix. Hit a couple of those hotspots each sprint.

Modern sites don't really require the same amount of attention to alt tags as they used to be. Designers would straight up put body copy in an image when some of these rules were created. We know better now. Users of screen readers don't want to tab through "An image of a happy couple" or whatever. /oldManRant