It gets pushed because that's exactly what
works. People aren't just drones. They eat up crappy pop music because their brains respond well to it and they buy it when it gets put up for sale.
Since I didn't have time to address the rest of your post before leaving today, I'll do that here.
Not always. Sometimes, the biggest successes have come out of telling the artist to do what they want. I'll use the Interscope/Nothing saga as an example. Interscope knew that they would screw up if they tried to meddle too much in Trent Reznor's (NIN) affairs. Because of that, they gave him Nothing Records, and proceeded to let him do things his way, with NIN releasing albums rather slowly. They quickly learned not to fight him after he won by threatening to leave if they didn't let him sign his first band to Nothing. Luckily for Interscope, that was Marilyn Manson. While they were meddling at times, Manson, Reznor and the rest of Nothing were mainly left alone. However, after Nothing folded, Manson stayed on Interscope, but left after his 2009 album because they wouldn't leave him the hell alone, and started "Hell, Etc." at Cooking Vinyl. So, how'd that turn out?
Or, in other words, you pissed off a cash cow, and he left. In fact, Reznor went completely unsigned a bit before Manson left. Interscope didn't know to stop meddling. Their best times came from when they knew to back off and let the artist do his vision. Basically, meddle in the new guy if you must. After he proves himself, back the fuck off, unless he's going to do something insane.
Well, some people still don't really like Manson's latest albums. I've actually heard more criticism than positive reviews in spite of the sale numbers (I was still tracking his work back when he was with Dita Von Teese, then that one girl who was way younger than him; yes, I do acknowledge current Manson by which chick he was dating). So the quality of his post-Interscope stuff (and even his late Interscope) is up for debate. It's not an either-or thing.
That said, Reznor is a minority; he's done plenty of Nine Inch Nails stuff, but he also collaborates with tons of musicians and singers, films, video games, and other ventures. He came onto the scene as industrial was starting to become popular, which let him hit it big. The fact that he can be a downright industrial virtuoso at times makes him a very good person to make music for works that require that kind of tone. He had already earned clout through being a major part of a relatively popular genre.
I'll admit, those are good. I'm not saying to not meddle. The "Sweet Dreams" single was forced by Interscope. However, that said, those were either massive, horrible backstory changes, the job of an editor, and in that one, I don't know if I like messing with his artistic vision, even if it was good for the franchise. However, an actor change like that is pretty normal.
The job of an editor, but it was an
executive who noticed the problems. When something or someone is a cash cow, especially if their vision is successful a few times, they tend to get protection from the editors. At that point, it really does take someone higher up the chain to come in and stop them if they're making a mistake, as they often don't want to listen to anyone else regardless of their position. That's the danger with trying to take the accountants and marketers out of the equation too much. Sometimes they're wrong, but sometimes they're really, really right.
You had to have skill. It was braindead, but it was skillfully made. It took talent to do a guitar solo. It does not take talent to do an autotuned song with computer-music. Rap, I will admit, takes skill. Autotune does not. Motley Crue had (and have, saw them and KISS in 2012) skill. Singing and instrument playing took skill.
Skill, but it was still the same content. They may have performed with more talent, but their message was exactly the same. They sounded good, but it was essentially pop music for rock and metal fans. Even Guns n' Roses (who made quite a few songs about the dirty life and the danger of drugs) had a few songs not for the thinking man, like "Paradise City". Rock and metal bands, talent or not, could still be just as brainless, misogynistic, and "party hard" as contemporary pop and rap stars.
That said, I hate rap even though I understand the difficulty of it. I can't rap on command and one of my friends is downright genius with how he does it. I just despise it as an art form.