The best alternatives to Wikipedia for iOS are Modern for Wikipedia, Everipedia, and Wikiyarn. If these 3 options don't work for you, we've listed a few more alternatives below.
Enhance your Wikipedia experience with a beautiful, clean, modern design that's fully customizable. Once installed, this free extension will simply apply the new look and features to existing Wikipedia article pages, without you having to do anything.
Everipedia is a publicly editable, free content encyclopedia and knowledge aggregator. Everipedia differs from prevalent encyclopedias and research databases such as Wikipedia and Encyclopaedia Britannica in that it does not require a standard of notability for inclusion in the database, which many consider to be the key problem with both services.
WikiYarn is an application to browse the vast knowledge of Wikipedia quickly and efficiently. It works as a research/reference tool as well as a knowledge recommendation engine made for everyday use and for the general public.