For YouTube it displays the YouTube menu on first right-click, then the Firefox context menu on second right-click for me. On Windows.
If that is not the case for you, something may be broken. Have you tried running Firefox without any add-ins already?
I think the bigger issue is them potentially losing their Google income.
They’ve failed to diversify their income with a bunch of failed subscription services, Google is in hot waters because of anti-competitive behaviour; they’re going to need something.
Which isn’t to say I like it. But “this is happening because they take Google money” is parroted beneath every slightly negative thing Mozilla does.