I understand what you’re trying to say, but Wikipedia is a fantastic resource for mathematics. “Pretty awful” is not a correct choice of words. But yes, much of it is written at beyond-undergrad-math level. And undergrad math is already advanced! And no I’m not someone with a math PhD talking down! I’m struggling through teaching myself undergrad math.
The only way "pretty awful" is incorrect is that it is too polite and reserved. Reams upon reams of pages are written completely at odds with Wikipedia's own style guidelines and common-sense expectations of what one might find in an encyclopedia. Unlike some famously dense mathematical texts, wikipedia maths pages don't even come with any of the benefits of brevity or focus. It's like a giant joke competition of who can describe every trivial thing in the most abstract and abstruse way except it got out of hand and the participants forgot it was supposed to be a joke. Mathworld and similar sites will help you much more with undergrad maths.
We’re saying much the same thing, it’s just that I find your and GP’s use of the absolute “pretty awful” to be hyperbolic and something of a loss of perspective. Remember what we have here: a free, actively maintained, accurate, comprehensive and advanced corpus of expository writing on mathematics. Adjectives that are missing there are “intuitition-rich”, and “helpful for undergraduates”. I do understand if you are disappointed with it. As noted, I (undergrad level) don’t approach it with an expectation that it will be my favorite reading on a topic.
