What's stopping you from going with Nim? Honestly curious, I have my own love-hate with that one, so I have some guesses, but I'd find it fun to "fact check" those and compare opinions :)
Prologue is the most promising one IMO, but it is still very new and its performance isn't as good. But I do keep a check on it.
Overall, Nim needs something like Lucky, Athena, Azu Toolkit etc to feel like a serious web dev language.
That said, I have always been thinking of rolling with just the stdlib stuff so I may do that one of these days.
I agree that a nice website would be great to have for Jester (and I do intend to create one), but I think you place far too much importance on Jester having one. Jester/HttpBeast is used in production by big web apps[1], why doesn't this inspire enough confidence and possibly even more than the other web frameworks you've mentioned?
I think there is an inherent bias that all humans have for shiny design, you should definitely keep it in mind when choosing a technology.
However, considering the huge amount of languages/webframework pairs (D+Vibe? Nim+Jester? Crystal+Whatever? Go? Rust? etc.) available today, it is understandable that people pick simple criteria like this to decimate their number of choices. The alternative to start playing with each tool for a few days to rank them and pick the best choice is obviously not possible.