Server response time (TTFB) was ~21 seconds — the browser waited over 21s just to get the first byte back from the server, before it even started downloading images/scripts. Everything after that (images, theme files) loaded in a normal ~400ms each.
That rules out your connection, CSS/JS bloat, or images — this is 100% server-side: the PHP/database backend (SMF forum + Oracle/MySQL) is taking ~20s to generate the page, likely due to server load, a slow query, or resource contention on their host.
Nothing you can fix as a user — worth flagging to the mods with "page takes 20+ seconds to respond before anything loads" so they check server/DB load rather than assets or caching.