Too much of everything, too little of anything.
First off i think Eurofans were a bit overly positive. A very common comment was basically "at least it's not gonna be last, it's gonna do better than Germany usually does" which spells doom. And in the end, it got the classic German placement.
The song didn't really appeal to metalheads, because it wasn't metal enough, it was only typical Eurofans who thought it would. Also, some of them might have been put off by the queer elements. Käärijä sucked up a lot of votes with his metal-punk-inspired energy, while those who wanted a "real" rock band voted for Slovenia or Australia ,who only got 20th place with 21 televote points anyway.
The juries, and mainstream televoters, didn't like it because of the silly chorus and the weak, unsteady clean vocals, which weren't that great in the NF either, but many overlooked for some reason. I guess people were impressed by his overall performance and charisma, but his singing was never really that good, in this song at least.
Then the staging wasn't spectacular enough. With a title like "Blood and Glitter", you could imagine drag queens in enormous alien space armor with wings or horns, giant jiggling breasts, spewing blood or fire from their mouths. Instead we just got a typical horror-rock performance with a bit of feminity added on like nail polish.
It wasn't queer enough to appeal to LGBT viewers, and if anything it may have come across as appropriating LGBT culture, kinda like Yohio was accused of in 2013. I don't know if any of the band members are LGBT - it frankly doesn't matter to the viewers who don't know, but it may have increasingly weakened one of their supposed strengths.
Overall, i think they could be pretty proud of their choice. They've gotten an entry that people actually talked about - even though it clearly failed to work outside of the Eurofan bubble. They need to pick artists that actually believe in what they're doing and understand Eurovision, and all their recent ones have failed on one or the other. Jendrik and Malik Harris were sincere artists who just didn't belong in the contest, while the others tried a bit too hard to fit into it and ended up bringing nothing of substance. I think this really was a step up in quality and ambition, it just didn't show in the results for complex reasons. Better luck next time!