The IPA is gibberish and I can't read it. Why doesn't Wikipedia use a normal pronunciation key?
The IPA is the international standard for phonetic transcription, and therefore the Wikipedia standard as well. Many non-American and/or EFL-oriented dictionaries and pedagogical texts have adopted the IPA, and as a result, it is far less confusing for many people around the world than any alternative. It may be confusing in some aspects to some English speakers, but that is precisely because it is conceived with an international point of view. The sound of y in "yes" is spelled /j/ in the IPA, and this was chosen from German and several other languages which spell this sound j.

For English words, Wikipedia does use a "normal" pronunciation key. It is Help:Pronunciation respelling key, and may be used in addition to the IPA, enclosed in the {{respell}} template. See the opening sentences of Beijing, Cochineal, and Lepidoptera for a few examples. But even this is not without problems; for example, cum laude would be respelled kuum-LOW-day, but this could easily be misread as koom-LOH-day. English orthography is simply too inconsistent in regard to its correspondence to pronunciation, and therefore a completely intuitive respelling system is infeasible. This is why our respelling system must be used merely to augment the IPA, not to replace it.

Wikipedia deals with a vast number of topics from foreign languages, and many of these languages contain sounds that do not exist in English. In these cases, a respelling would be entirely inadequate. See Wikipedia:Manual of Style/Pronunciation for further discussion.
The IPA should be specific to a particular national standard, and the national pronunciations should be listed separately.
Listing multiple national pronunciations after every Wikipedia entry word quickly becomes unwieldy, and listing only one leads to accusations of bias. Therefore, we use a system that aims at being pan-dialectal. Of course, if a particular dialect or local pronunciation is relevant to the topic, it may be listed in addition to the wider pronunciation, using {{IPA-all}} or {{IPA-endia}}.
The use of /r/ for the rhotic consonant is inaccurate. It should be /ɹ/ instead.
The English rhotic is pronounced in a wide variety of ways in accents of English around the world, and the goal of our diaphonemic system is to cover as many of them as possible. Moreover, where there is no phonological contrast to possibly cause confusion, using a more typographically recognizable letter for a sound represented by another symbol in the narrow IPA is totally within the confines of the IPA's principles (IPA Handbook, pp. 27–28). In fact, /r/ is arguably the more traditional IPA notation; not only is it used by most if not all dictionaries, but also in Le Maître Phonétique, the predecessor to the Journal of the IPA, which was written entirely in phonetic transcription, r was the norm for the English rhotic.