Even the Facebook mobile web part that has been developed in React, the people search, feels rather slow on all my mobile devices (incl high end iOS amd Android devices).
IMHO It's still faster than most webapps on mobile. I use an old Alcatel with Android 2.3 to benchmark performances on low end handsets and Facebook performances are ok compared to Gmail or even Google search which takes 3+ seconds to load just to display a search box. I think Facebook has managed to do an acceptable job if you compare their app to other web apps.
The truth is, the mobile web space is not a good as developers expected it to be in 2015 unless users visit websites with expensive devices, which most of them do not. Making a website responsive , while being an improvement, doesn't make it automatically mobile friendly.
