I would agree that making a progressive rock song into a power metal one is not the greatest idea, and he does an okay but not great job with it. However I would certainly have to take issue with your contention that they did this for attention. Axxis are a huge band --- I have all their albums --- and certainly very well known in the genre. They don't need YouTube postings for "fifteen minutes of fame". I would say (though of course I dont know) they just heard the song, liked it and wanted to cover it. I dont' really see anything wrong with that. It's generally in the same basic genre. What I have a problem with is someone taking a song from one genre and covering it toally outside that, like maybe taking a reggae song and playing it in disco, or a metal song and making a pop tune out of it. "Don't fear the reaper" springs to mind.
But I don't have a massive problem with this. Again --- and I'm not saying you stole my idea, it was probably an unoriginal one anyway --- I do this section in my journal, called "Run for cover", where I look at unusual cover versions. Admittedly, not all are classics, but I would not agree that classics should be exempt from being covered, provided the cover is good and done in respect. What I would have a problem with is someone totally ruining a classic --- like maybe sampling "Stairway to Heaven" or using "Free bird" in a -- oh, wait! --- or using it simply as a way of, as you contend above, getting attention and/or fame. Axxis are not doing this: they have been around since the late eighties, and have sold millions of albums. The one you mention here is a whole album of covers, and I would assume songs that mean something to them, so the idea of using it to get themselves known is completely wrong.
I also have an issue with your assessment of Bernhard Weiß's singing. He's not the best metal vocalist by any means but he's not the worst. He's certainly no Jon Anderson, and really I would agree that his voice does not suit that song. But he's definitely able to sing. Also, can you sing chords? I don't think so: notes yes, chords no. So far as I know.
Here's one of Axxis's better songs in my opinion, just so you can see how he can sing. They have piles of original work; not sure what issue you have with that?
Of choice I would have said no, not this song, though think yourself lucky: on the album I see they do Phil Collins, The Polcie and even Celine Dion!!!
But the choice to cover a classic doesn't invalidate them as a band, and they have plenty of great albums to stand to them. Maybe you should give them an unbiased listen?