Why this happens.
Speed problems build up one plugin, one tracking script and one uncompressed image at a time. Nobody owns the budget, so the page gets heavier every year.
What not to do
[YOU]: the most expensive performance mistake you have seen a client make before calling you.
How I’d approach it
I measure first, find what costs the most seconds, and fix hosting, images, caching and scripts in that order, then set a performance budget so it stays fast after I leave.
