Really curious about the state of agency SEO services these days. Do you guys just do the standard on-page tweaks, or is there some backlink building too?

I once looked into the backlink profiles of a successful SEO agency's clients and I discovered a makeshift PBN going on; they had 100s of sites ready to go and would just add client links to them. In predictable patterns (# of referrer pages would jump weekly etc.) Presumably this is fine because it's working and this is how they promise position increases / page 1 for certain kw etc.