Android visual standards are a hot topic - just check the comment section every time a point of contention in Material Design springs up. One of the most contentious is top tabs and slide-out menus, as featured in Android since Ice Cream Sandwich, versus bottom navigation links, as tends to be popular with lazy iPhone ports (though they're actually part of the documentation). The latest update to the official Wikipedia app indulges in a little bottom-nav action, and it's... okay.
The toolbar is meant to quickly place the most commonly-used tools within easy reach on the homepage, articles, et cetera. It shifts depending on which part of the site you're looking at: the homepage has the main "explore" interface, your personal reading list and history, and points of interest near your GPS location. On individual Wikipedia articles the bottom links shift to a bookmark icon, share button, translate button, quick search, and an activator for the slide-out menu. The latter is different from the drop-down menu, and that's less than ideal visual design, but the double-menu setup was present in previous versions of the app - see below.
An older version of the Wikipedia app from 2015.
The only other change in the latest version is an option to search through the specific contents of your reading list and a bug fix for the app's dark theme. Wikipedia is, naturally, a free download with no ads.