I will agree here. In fact, OSM instance opening random thread even seems to load noticeably faster (2.5s largest contentful paint) then discourse own instance (4.2s largest contentful paint).
Thus I would suggest that people who are having performance issues on community.openstreetmap.org try meta.discourse.org too. If that instance is noticeably faster then OSM one, than there are things that can be addressed here. If it is about the same slowness, than any request for performance improvements should be taken with Discourse developers.
This webpagetest.org waterfall graph shows about half the time of that 8 seconds is just javascript pegging up the CPU without any data even attempting to load. You may also wish to test and compare your hardware+browser rendering speed in Speedometer 2.0 (e.g. my laptop gets 112 runs/min in Firefox, 178 in Chromium; P30Pro only 35 in IceCat and 40 in Firefox Klar; and Galaxy S II only manages 7 runs per minute).
Discourse is unfortunately Javascript-based beast, which means that it offloads much of the work to the client, which means the slower the device (read: mobile phones, especially the ones that are not newest top-of-the-line ones) are likely going to suffer.
For example:
-
on my Huawei P30 Pro, clicking on random no-yet-visited thread on OSM instance on 50Mbps Internet link, takes about
2.2sto fill the screen with data (i.e. largest contentful paint). -
on my old Samsung Galaxy S II, using that same Internet link, that same page shows in about
3.8s. (and complains about unsupported browser, likely meaning not all functionality has been loaded. It displays article just fine, though). -
on my 11th Gen i5-1135G7 @ 2.40GHz laptop, again on the same internet link, it shows in about
1.2s.
Grim statistic offered by Chrome Lighthouse (available via F12 keypress) while it evaluates performance say than almost 70% of mobile pages take almost 7s to load (and then proceed to say how much conversions you are likely to lose because of that).