Think of it like f2p games- switch to f2p actually makes MORE money to the industry, it's just more continous and less front loaded.
Most popular writers on RR and SH make over 10k$ a month including amazon book sales. Though it depends on your model and marketing skills. If you want to feed family by writing you are unlikely to succeed, period - in one of his lectures Brandon Sanderson talked about how, when he graduated from fancy university with writing degree, out of his class where all people tried to become writers full time, only something like 20% succeeded. And that was super high. And before the self-publishing days. Path of art is always hard.
And don't misunderstand it as me saying that printed books suck or anything, or as hate towards publishers, but man, if you believed it was ever easy to earn money writing or even remotely likely, you are naive. Even famous authors had to earn money in other ways for years before becoming successfull writers- Hunter S Thompson, D. F. Wallace, Hemmingway - they had to be reporters, and/or write short technical stuff. People who send novels to big publishing houses and got accepted, and magically became able to earn money by writing are exceptions of exceptions.
You also seem to think that serialising novels is somehow less, shit ton of famous novels (and respected) were serials.. just serialised in literary magazines that sold books chapter by chapter. "I Robot", (many early asimov works actually?), I think many works by Lovecraft, or with traditional literature for example Lalka (noble prize winning, sorry if you don't know it but it's super big deal in my country :P)
Video on publishing: