More pages is not more authority
A site with four hundred pages of which thirty are good reads, to an engine, as a site with an uncertain relationship to quality. Removing the weak ones concentrates the signals rather than discarding them.
The three categories worth removing
Pages that duplicate a topic another page covers better; pages stating facts that are no longer true; and pages that were published to hit a keyword and answer nothing. The last category is usually the largest and the easiest to identify honestly.
A page that answers nothing isn’t neutral. It competes with the page that does.
Merge before you delete
Most weak pages contain one good paragraph. Fold it into the page that owns the topic and redirect — you keep the substance, remove the dilution, and strengthen the survivor. This is the consolidation argument applied backwards to what already exists.
Redirect, don’t vanish
Deleted URLs with no redirect lose whatever authority they had accumulated and produce errors for anything still linking to them. Point each to the closest surviving equivalent — never to the homepage, which reads as a removal.
Check what is being cited first
Before pruning, ask the engines your category questions and note which of your pages appear. Occasionally the page you were about to delete is the one being quoted — rarely the page you are proudest of.
Make it part of the review cycle
Pruning once produces a clean site that re-accumulates. Adding “what should go” to the same review that checks whether facts are still true keeps it from becoming a project again.