Try loading up an image on a different instance, or browsing that instance from a different instance. If you can figure it out, it's as slow as molasses.
That said when I see posts linked to Mastodon on HN I do notice that maybe the HN Hug of Death hits them hard as they are noticeably slower to load than my day to day interaction with Mastodon, maybe this is what you're seeing?
I'm sure it's fine if both servers have the resources but visiting a small instance from a different small instance and all the images load really slowly.
