Any part of a song, be it the lyrics or the bass line, is important in comprehending it fully. You seem to like songs in which lyrics are of more importance and that's of course your choice. But a lot of people prefer a song that will speak for itself. Just like when I first heard Le Ciel there was absolutely no need to look up the lyrics to know what it was all about. When it comes to MM in general I feel like Gackt's lyrics especially are just redundant if not misleading.
So saying that not knowing the lyrics means the song is going over your head is entirely untrue and it seems like you, understanding the lyrics, are missing out on a lot we don't seem to be. I absolutely adore the fact that I can listen to Klaha's voice as an instrument and not have the lyrics distract me. Even though his lyrics are beautiful and I always enjoy reading them. And I'm sorry but as others said I listen to music from many parts of the world and I don't see how I need to know all those languages to appreciate it. It would have been nice to, yes, but just think of what I'd be closing myself to if I gave up on them just on account of that.