I guess I'll take the pro-translation, anti-localization stance. I think the tendency for groups to insert random Japanese words that were easily translatable was silly, but keeping the Japanese words that don't translate easily helped foreigners get a better grasp on Japanese culture, often for fairly important aspects.

You could translate 'shouganai' is 'it can't be helped,' but that oversimplifies something that is more about the mentality of the person being inconvenienced. There's a lot of context missing - the use of shouganai or shikataganai is more about the act of shrugging off what occurred and moving on to the next thing, with a tinge of fatalism about the whole thing. If you miss out on the last item on sale at the supermarket and you say shouganai, you're not saying 'Well, I should have shown up earlier' - you're acknowledging that it just wasn't mean to be. 'Kawaii' is similar - you could just translate it as cute, but it's both a broader and narrower term than what we mean when we say cute in English. There's cultural specificity to it, which you could chalk up to being the same "cute" just dependent on culture, but would miss the mark - there are things that Japanese people would generally find cute in the English sense but not kawaii, and things that are kawaii that we would not describe as cute. Things like honorifics being included helped understand the different levels of politeness, which was important context for conversations, particularly in dramas that were heavily character interaction driven.

The 'trollsub' groups were obviously a reaction to fansubbers going overboard and ending up with subtitles that might as well have been the delirious rambling of someone spewing out a mixture of Japanese and English words in a sentence, but I think they were just as much of a problem, and I think crunchyroll suffers from a similar issue.

Yes, truly understanding everything would require not only becoming fluent in Japanese but also studying the culture and history. But there's a happy middle ground where you can learn some of the most common and important bits and broaden your horizons and knowledge of other cultures. It's not necessarily about being respectful to a cartoon - it doesn't really matter whether or not you think there's particular artistic merit to any specific anime or the genre in general - but being respectful to the underlying cultural concepts that you see in it.

The same is true in reverse - there's lots of words in English that are better served being given as-is vs. an attempt to translate. Serendipity is almost the reverse of shouganai, and you could translate it in a lot of languages as something along the lines of 'happy accident', but similarly, leaves out the fatalistic implications of the word. Or bandwagon - translating it as 'Following the trend' or similar isn't going to capture the opportunistic and temporary connotations and semi-denigrating nature in which it tends to be used. Schadenfreude, anyone? C'est la vie?

Any time you're making something available to people in a new language, I think it's important to not insult the viewer/reader/listener/whatever's intelligence and be willing to try and teach them new things.