Done something similar recently. Site was suffering from Nov 2019 update and traffic crashed from 50k monthly to 8k per month. It had thousands of pages and a lot of keyword cannibalisation which I thought was the main issue. We identified which are the best ranking pages, deleted crap pages, pages with decent content we decided to merge with the better ranking pages, applied 301s on posts with links but no traffic to a relevant page. Just general content cleanup. 2 months later the traffic is now 130k monthly. So I do think there’s a general “quality score” for a site, that or the rankings just recovered due to consolidation of links from multiple pages on the same topic to a single page, and/or creation of bigger, longer, more comprehensive content by merging multiple contents together into a single post. Another major thing we did was also to fix crawl depth and made sure every page was no more than 3-4 clicks away (previously some were 8 clicks deep). Previous to that I just tried to optimise the existing content with POP, cognitive, surfer but didn’t have much luck with the 20 pages we tried it on. We also tried a bunch of links to those pages and it didn’t move the needle either (site is already DR 60+) so i’d probably attribute the recovery to the content clean up.