Well it is Free Software (<https://codeberg.org/teddit/teddit>, AGPL license (best license)), so anyone who is interested can do some profiling to see where the slowness comes from. Without doing any of that myself I would hazard a guess that the issue would be either of:

A: The Reddit API being slow or rate limited.

B: The site being hosted on a cheap VPS.

If the second issue is at play you could speed things up by running it locally (the README file includes instructions to do so with either Docker Compose or directly via Node).