It’s because I choose to put my efforts and funds towards other good causes which I value more. And I think that’s perfectly reasonable.

Reasonable, but, I would argue, wrong. Why not limit your philanthropy to the one cause you value most? You could then say to your second favorite charity that it does good work, but you choose to put your efforts and funds toward another good cause that you value more. But you don't do that, do you? You give to "other causes," which means simply that Wikipedia doesn't make the cut.

I daresay that everyone has good causes they value more than Wikipedia. I am pretty sure that Wikipedia could not survive on donations made only by those who value it more highly than anything else. Organizations like the United Way exist precisely so that we can fund good causes we don't even know about, much less "value more" than than some others.

Wikipedia is a sort of commons, and not contributing to it is analogous to overgrazing the meadow. I send them $3 a month so that it can continue to exist. By my lights, that makes my donation very effective in making a difference, something that may be even more important than whether the cause itself is one I value above all, or even most, others.