Noindex vs delete
Noindex tells Google not to show the page in results but the page still exists and may still factor into the site-wide quality classification. Delete (with a 410 status) is a stronger signal that removes the page from Google's consideration entirely.
For pages with no business value and no backlink equity, delete and 410. For pages with backlinks but no quality, 301 to the most relevant remaining page. For pages you want users to access (logged-in tools, internal docs) but not Google, noindex is the right tool.
How aggressive to be
On a healthy site, aggressive pruning is unnecessary — focus on improving the next batch of pages instead. On an HCU-affected site, aggressive pruning is often the highest-leverage action available; in our engagements, recovered sites typically removed 30–60% of indexed pages.
Site owners resist this because it feels like throwing away work. The classifier reads the site-wide quality distribution; pruning the bottom of that distribution improves the average even if the pruned pages were sending some traffic.