Just a little trick..
Remove all widget call you find in it (sure, if you dont use it).
Thank you for that tip!!!
I just tested it.
A page that uses the shared/_productbox.cshtml had a 2.08 TTFB and a Lighthouse speed score of 31! Ouch!
After removing all the HTML.Widget instances, TTFB was fixed and the Lighthouse speed score jumped to 50.
I will now go though all the razor views and remove the unused HTML.Widget instances.