1) Not like there's proof in VK, but the speed at which some bands pump out releases and the repetition/overuse of riffs and other elements can be a sign of ghostwriting. Also, when you see kids in the scene who aren't that good playing on stage yet are credited for what they play makes me wonder if they really did write it.
2) I think the whole scene is idol kei now. The way bands are put together, managed and marketed is very idol-ish. I'd say VK bands that are less "idol" would be those who put out releases less often, don't focus their sales on cheki and spend more time touring than doing fan-meet events.
3) When was the first instore? Not sure when VK evolved into what it is today, but I'm sure it was a while ago.
4) What is good music? I think there is good music and bad music in VK, just like in any other genre. And personal enjoyment does not atone for quality. I may not enjoy Morrie, Sukekiyo or Kiyoharu's works, but it is undeniably good music. Whereas I may like a lot of indie artists I consider to be musically mediocre. All in all, if I didn't enjoy VK I wouldn't be here.
5) VK does not rely that heavily on the music genre to survive. As long as there's scantly dressed pretty men wooing teen fans into spending their yen, the "well-being" of the scene is preserved. As overseas fans, we focus mainly on the music, because it is really all we can focus on, out of all VK has to offer as a scene. In Japan it is slightly different. You could enjoy the social experience, the fan events, the fashionable aspect, idk.
6) Because I have shitty music taste? LOL. I can't remember how I even got so hooked on this scene. It gives me versatility in a way many western rock artists don't. Bands don't always stick to a genre and blend a lot of styles to find their own. I don't know much about music theory but I know Japan uses a distinct... scale? for writing their music and I find it pleasant to my ears. I also tend to focus a lot on bass and vocals. For the first, I've found more interesting bass-lines in Japan than overseas, where it tends to be a filler instrument. And for the latter... Have you seen those "sounds just like Ruki" comments on various YouTube videos? Well, they do, because Japanese men tend to have a similar vocal range that just happens to tickle my fancy. There's also the thing that with Japanese I can easily ignore corny lyrics because I simply do not fully understand them. I don't look them up either, I can live without knowing if I'm being insulted.
I come from the pop/rock scene, never really went through a western punk/metal phase in my teens year. I grew on 80's rock and 90's pop and I got used to catchy sounds accompanied by guitars, and it's what I look for in VK; poppy choruses with clean vocals and harsh instrumentals + lyrics I don't have to feel embarrassed about. Something that western metal and pop often fail to give me. The visuals aren't really that important to me, since I never watch PVs, but the androgynous beauty pleases me a lot when I do want to watch it tbh. As a big plus, I greatly enjoy the whole VK culture in Japan. I gotta say I love going to a small gig without being pushed around by huge dudes or drowning in the stench of weed and going to instore events and such.