Distrust of constitutional courts (and the like) as a case for their democratization

In majority of today Euro-American states there exists an institution (in many examples a constitutional court) with jurisdiction over at least some acts of a parliament, empowered to derogate these acts or their parts (as unconstitutional). There are opinions today that those institutions are going or turning to be “political”, resembling the parliamentary politics’ discourse.
I want to, firstly, justify this opinion. Secondly, I want to argue, that the procedure of vacancies’ filling in the institutions shall be democratised and made transparently political. Moreover, that the census for candidates (which today in most cases are strictly legal abilities) shall be widened. I want to ground my opinion on epistemological inquiry concerning the difference between beliefs, which we ordained by our own reflection, and other, to which we were introduced from external source (even with proper justification); the inquiry I find as one of the most important arguments for democracy as such.