Then just stop doing it. If science needs publishers, scientists will soon notice. If not, well, good riddance!
Frankly, ACM just kills it's own value proposition. You publish with ACM, or IEEE et. al., because they propose greater reach. If scientists realize that noone pays the ridiculous amounts of money and usually go to archive.org instead, they will soon realize that they don't need ACM for publishing.
Soon after, free, or very cheap, open access journals and collections will be the go-to default. If the traditional publishers have any more value to add than a searchable catalog and a barely functioning citation index, they will compete. But I doubt it.