The problem is not with the web-pages; not that they are blocking the action on plan.
Evernote clipper is failing even on Wikipedia pages.
Try to clip this page: https://en.wikipedia.org/wiki/Zermelo–Fraenkel_set_theory, you will find all the mathematical formulas are missing.
- both Chrome and Firefox extensions have failed me, on the mac.
This problem of missing parts (images and formulas) for ages.