> Technically it is correct, but in doing that you lose the essence of the word “roman”
This isn't specific to concepts like "Bildungsroman." You're essentially saying "this word isn't just a word, but a word with implicit cultural context."
That's true of pretty much every word. Hell, translating "ao" from Japanese, you'd think is so simple: blue. Except it can also mean green because in Japanese there is less historical, cultural distinction between blue and green. So obviously green traffic lights are called "blue" in Japanese, not green.
You'll never get a perfect translation of anything that's longer than a couple words. The point of translation is getting close enough. Translating Bildungsroman as "coming of age novel" gets you so close, that if your conversation hinges on the actual nuance, you're almost assuredly talking to someone who will understand what Bildungsroman means, so you just use that word.
EDIT: One of my friends at uni did his thesis on the difference between Japanese "natsukashii" and English "nostalgic." I've always thought about that as the perfect example of how any simple translation is fraught with cultural complications. There are certainly things I would call "nostalgic" but I'd never call "natsukashii," because nostalgia can come with sadness, but natsukashii never does.