This is not related to speed of hosting, but speed of client. If you visit your forum from fast device, it will load fast. If you have slow device, it will be slow. According to your screenshot, tests were made by emulating Moto G4 - this is phone from 2016, so it is quite old, and even then it was more like a budget-level device. So metrics reported by Pagespeed are only relevant if your forum is visited mostly from slow devices (and even then they may be irrelevant, because after initial slow load, further interactions with forum should work quite fast). Removing some extensions may improve situation a bit (by reducing amount of JavaScript and required CPU power to execute it), but it may be hard to get good results here due to SPA nature of Flarum.
