As you saw, my forum is fairly quick and it is on shared hosting. I'm currently (I must throw currently in there because minds change) a big fan of managed, shared hosting. It's almost a requirement if you are not a real developer and instead just like creating communities (like me). If you pick a good one, they have usually spent many, many years optimizing their set up. My current shared host (again "current" because I've been known to hop around) has been around for many years, is popular with good ratings, relatively inexpensive considering I don't have to set much up, they have their own built in speed features, plus integration with CloudFlare.
In short, the way I keep my Flarum(s) almost as fast as discuss.flarum is a combination of a great web host and CloudFlare aggressive caching.
I'm also proud that my forum gets an "A" grade from @clarkwinkelmann's lab: https://lab.migratetoflarum.com/
If I instead went the "modern?" route of using AWS, or VPS/cloud/whatever you want to call it hosting, my forum would not be as fast because I would not know how to optimize it. 🙂