Of course we can't answer your question as to how you could expect to understand continental texts. Don't know you, after all.
Still, some comments might be relevant.
Personally I operate by this principle: I will not reject as meaningless, misguided, mistaken or whatever any philosophy or philosopher that I
haven't read  myself. I really recommend this principle, especially as the history of philosophy contains instances of
top ranking philosophers testifying to the meaninglessness of work that certainly makes sense to lots of people, myself included.
I share your high opinion of Williamson and I confess I find some of the Continentals more accessible than some of
his work. Part of being a professional is not letting others decide these matters for me, IMO. I don't care how acute they are.
I have the hard-won ability to make
such determinations myself and I think it's part of intellectual fairness to do so.

Testifying to the worth of Continental philosophy are these facts: mainstream philosophy has been much affected by, and incorporated,
ideas from Continental philosophy, e.g.  intentionality, bad faith, phenomenology, Brentano's problem, bracketing. Further
analytic philosophers sometimes draw heavily on Continental philosophers (e.g. Searle 'Intentionality' acknowledges a considerable
debt to Heidegger), write books about them, teach them in analytically oriented graduate seminars, and so on.
Plainly these philosophers feel they understand the texts well enough to make good use of them, and find them rewarding,
so perhaps you will too. It may take some hard study, of course.