If one's goal is to travel to Japan or to research their culture, knowledge of Japanese and/or English is required anyways. In the latter case, one will be positively surprised that there are only a few rules specific to Japanese to be learned to be able to read with some degree of accuracy.
One might object to the dominance of English as a lingua franca, but actually any other languages being the lingua franca would dominate the Romanization system as well, and that would lead to similar issues for speakers whose writing system works differently.
Kunreisiki is not a system dominated by any particular lingua franca; it's a system that directly reflects Japanese ways of writing Japanese. One could imagine e.g. a Spanish-influenced romanization system that would represent the は-line in a way that corresponded to Spanish orthography becoming popular in a world that was dominated by Spanish as a lingua franca, and that would have the same problems that Hepburn does. But Kunreisiki really is "neutral" in that sense.
Hepburn may not be an ideal match for German, but it's still a better one than Kunrei-shiki. I'm fairly sure there is no language in the world whose pronunciation of Latin letters matches the latter (hah!).
The only thing Kunrei-shiki has going for it is that it's more regular and can be more easily matched to kana. It's easier for Japanese kids to learn. But they are not the ones who are going to use it primarily.
You could use different romanization systems for each foreign language, and there are some (there is one for German where あいち is "Aitschi"), but that doesn't end up serving anyone well in a globalized world with an Internet.
Japanese does not naturally include distinct U/V letters and does not have a first-class concept that needs to be written with a J; the official way to romanize that place name is "Sinzyuku" and that's morally equivalent to a traditional-Latin "SINZYVKV". W does exist but is decidedly second-class and declining (only the "Wa" sound is really heard any more; I suspect it will go the way of obsolete phonemes like "Ye" and "We" soon enough).
> this would likely be better understood as a form of Japanese spelling reform rather than "Romanization".
It makes no sense as a way of spelling Japanese. It's about standardising on anglicising Japanese instead of romanising it.
I don't use Romaji much but I learned the Japanese syllabary ~35 years ago so translating Hepburn to correct pronunciation doesn't involve any conscious thought on my part.
Irish pronunciation may be local, but the orthography is very consistent. I actually felt there was a lot in common between Kunreisiki and Irish - at first blush it's very confusing for a native English speaker, but once you get over that initial reflex and read it according to its own rules it all makes sense.
> I don't use Romaji much but I learned the Japanese syllabary ~35 years ago so translating Hepburn to correct pronunciation doesn't involve any conscious thought on my part.
Right, but doing that will paper over the issues with any romanisation system. What do you find worse about Kunreisiki?