Every addition costs something.
THE PROBLEM
Each plugin loads code, styles, scripts and database queries on every page.
Twenty plugins is not twenty times slower than one, and it is meaningfully slower.
WHAT TO AUDIT
List every plugin For each, ask what it does and whether you use it Deactivate anything you cannot justify
WHAT PEOPLE FIND
Plugins installed to test something and never removed Two plugins doing the same job Plugins for features no longer on the site
HOW TO TEST THE EFFECT
Deactivate one, measure, reactivate.
Tedious and it identifies the expensive ones.
WHAT TENDS TO BE HEAVY
Page builders Slider plugins Anything adding scripts to every page Security plugins scanning constantly Related-post plugins querying the database
WHAT TO DO ABOUT A HEAVY BUT NECESSARY PLUGIN
Check whether it can be limited to the pages needing it.
Some optimisation plugins allow that.
BEFORE DEACTIVATING ANYTHING
Back up.