ACP has been mostly pushed by Inrupt, the company Tim Berners-Lee founded around Solid, and which is mostly focusing on enterprise customers. (Disclosure: I used to work there a couple of years ago.) It's the method their Solid instance https://pod.inrupt.com uses.
WAC was the initial access control spec for Solid, and is still used by the main community-used server, https://solidcommunity.net.
So they're both the main focus for an important cohort of people, unfortunately...
@VincentTunru @jg10 uh oh