As an SF author once pointed out: "It's. Not. That. Simple. EVER!"
Great music communicates. It is therefore not fair to complain about artists using whatever means they can find to ensure their messages reach as wide an audience as possible.
Freetards will naturally argue that this means you should give your work away for free and get the greatest exposure. Except...
... how are people even supposed to know _of_ your work if you have no talent for self-promotion, nor enough money to pay a promoter to promote you?
And what about the billions of people who do not yet have cheap, fast internet access? (Yes, that's right: "billions". The internet, as the West knows is, is not as ubiquitous globally as some people like to think.)
Sturgeon's Law states "90% of everything is crud." One of the *purposes* of publishers and their A&R people is precisely to filter out as much of the unpopular crud as they can. They provide an editorial screening service, with a guaranteed minimum level of technical quality. (As for the actual music: there's no accounting for taste.)
The West's ageing population is another of the reasons for the fall in overall sales, but this is a distinct issue, only tangentially connected with the disruptive technology of the internet.
People are living longer than they used to, and they not only have more time to spend, but also their retirement money too. (That's why all those hoary old has-beens keep coming out of retirement.)
But probably the greatest issue is that there's simply not much technical innovation in music any more:
We've just seen a truly spectacular century for music production and performance technologies, which has taken us all the way from orchestral (so-called "classical") music, through Big Band, Jazz and Swing, right up to electric and electronic instruments and production studios—including the invention of sampling (1940s, "musique concréte") and audio synthesis (beginning with the discovery of electricity and invention of instruments like the Theremin).
My generation grew up with the BBC Radiophonic Workshop's musique concréte (and, later, electronic synthesis) output ringing in our ears during the 1970s, followed by the rise of the synthesiser keyboards, electronic drum kits and samplers. The rise of computers and DSPs brought about even more changes, until today, pretty much *any* conceivable sound is relatively easy to create.
We shall not see the 20th Century's like—in music's evolution, at least—again.
Today, all we see from the musical technology companies is refinement, not revolution. The pioneering days of seeking new "sounds" are drawing to a close. Music industry simply has no more new worlds of sound left to explore through technology alone, leaving the music itself as the only differentiator. This is as it should be, but the older industry veterans will likely take a long time to adapt.
And so will listeners.