I'm ambivalent too, i.e., I agree with your original comment but also, personally, frequently find Wikipedia's "general purpose encyclopedia for specialists" useful.

FWIW, there's Simple Wikipedia (https://simple.wikipedia.org), but it is, quite frankly, terrible for learning about anything of a mathematical nature beyond high-school algebra.

Perhaps Wikipedia should add a "Learn About This" section to math, physics, engineering, and hard-science pages?