The google robots rank wikipedia.org as 'not mobile friendly'
The reason it states is simple. "Links too close together". Specifically, it means the links to the hundreds of wikipedias in other languages.
Screenshot taken from:
https://developers.google.com/speed/pagespeed/insights/?url=https%3A%2F%2Fwikipedia.org%2F&tab=mobile
In total the google robots identify 316 links that are 'too close together'.
I propose we add some margin or padding to these links as well as increase their font-size, so that they are actually usable on mobile devices.