You bring up a lot of stuff and some of its wrong. Basically traditional publishing is dead, but those places might help get you into conventions and stuff to sell your book. Generally though regular old publishing houses are really poor at helping authors and really tend to open them up to scams like paying to join a club so you can vote on the Nebulas and get nothing else in return. Publishers don't give you any help with insurance, taxes, and any other number of the side aspects of being a writer. Writers that work hard get ahead and most already in the traditional publishing world would self-publish if they could.
I personally think books are going to get more popular as people get bored of shitty videogames and movies. A book is literally like the most expensive and personal movie without any compromises or shortcomings that either of those first modifiers normally require. And self published digital books can be sold for like $4 and still come out good for the author so it's a low investment for prospective customers.
I feel like if you like writing you should do it because you enjoy doing it, but also the goal of writing is to be read. It's just imaginary without that. But writing just for money sucks, I remember this reddit for erotic writers existed and I read through their stuff: a) they escaped the world of a dayjob but they had to spend the same amount of time looking up fetishes to make books on and b) they basically all needed to write a book a month (it's porn so it's not like a real books but still they needed a new product every month) and c) they had a big problem with categories. Like maybe there's not a lot of inflation erotica so they would start making that and it would sell well enough for a bit then get overcrowded and they needed to move to piss books. Anyways they wrote so much for work none of them actually worked on that good novel they wanted to write.
If you really want to make money it's trying to find an unfulfilled market need, it's research, it's a lot of extra stuff. Very few people get to be Stephen King and write piss and get paid for it.
Write because you enjoy it, put it out so it can have a life, try and get it reviewed to help that goal, and possibly buy some ads for it.
Humanity is over, so…
Unironically get with an indie publishing house. Unlike major publishers they're not in a position to strongarm you, but unlike self-publishing they can still hook you up with things like cover art, marketing, and printing.
It's definitely true that less people are reading new books though. There's not a lot you can do about that except shill your book here like that anon did on /tv/ for his movie.