Advertising is everywhere. Not just on dA. It's on just about every page you visit. It's on the highway, on the tv, in the bar, and I'm pretty sure you mentioned making shirts to advertise your band. You also have an advertisement in your signature.
Even if you are not making money off it, it is still an advertisement. Your link leads you to your music site which also has ads. Small but they are there. Twitter, facebook, each icon is in itself a small advertisement. The page also advertises other bands with music similar to yours.
Sure dA has advertisements, but someone has to pay for the servers that millions of people get to use for free with no upload limits or caps, and someone has to pay the staff who run the place. So what if they make some money on the side. It is no different than you selling your shirts with your band name on it. People see the shirt, find your band and hopefully buy a CD. Everyone walking around wearing your tshirt is a walking billboard for you. You used to design these all the time.
Yes advertising can be annoying but it's not going away anytime soon.
As for dA's soul. I think there is plenty there with all its diversity and drams included. You can't be this huge and be perfect. Yes there are more niches and little sub parts with the help of groups and what not, but with a site this big, it makes it that much easier to connect with the people who are interested in the same things you are. If you don't get involved then you don't find the hidden gems of this place.
People complain about the number of teenagers and the anime, Pokemon or latest My Little Pony craze on here too. We were all kids once and most of us were not drawing fine art. We were drawing what we saw on tv, or in the theaters. There are tonnes of great professionals on here who still draw this stuff too. Not every kid is going to be famous for their art from here but someone could be the next Disney. For those that discover more from the art world and leave their pony doodles behind as time goes on, we could have our next Emily Carr or John Paul Thorton.
Isn't the point to be sharing and helping each other grow? Even that kid who seems obsessed with ponies? I find too many people focus on the negatives of this place. Every place has negatives. Look past the trolls and that silly advert in the corner no one is forcing you to click on, and focus on the people and the art. It far outweighs the advertising and the trolls.
The future is always changing and so is dA. The admins don't make dA what it is, we do. They simply provide the tools.