A potential issue with WordPress is, because of its fragmentation, to be unable to incorporate the newer technologies before its competitors and so become eventually obsolete. The last couple of years, new web technologies such as Service Workers (to create Progressive Web Apps) or CSS Grid have been introduced, yet these have barely been adopted within the WP ecosystem (or so I believe). Similarly, WordPress does not offer a standard way to implement modern techniques to make websites load faster, such as code splitting (to load only the needed javascript/css and nothing more), server-side rendering (for those cases in which the view is rendered with javascript) or pre-caching static assets in the browser through Service Workers.

Lately, each time I watch some presentation showing off the latest techniques/technologies to optimize websites (eg: Progressive Web Apps across all frameworks - Google I/O 2016 by Addy Osmani) I'm thinking: "Nah, we can't do that... or that... or that..."