I think the biggest problem with comics right now is that everybody is giving them away for free on the internet, including me. The business model for web comics is give away the product and build a fan base and hope that eventually people will pay you in the future via pattern, kickstarter or by buying a physical copy. That works for some people but it doesn't work for a lot more.
I've been posting my comic here for a couple months now and I've only got a couple of subscribers and likes here and there. But likes aren't the same as an actual sale. My full comic is currently available for sale at the moment but why buy it when I release a new page every week?
Overall the mistake all artists made was making art for free. Not just in comics but in illustration, graphic design, and etc. It lowered the whole value of artistic abilities. People now expect art to be free and complain about how comics now cost $5 when they buy everyday their god damn coffee for the same amount with no question.
Right now comics and art are in a damned if you do, damned if you don't situation. If you don't give away your comics for free, well, there are thousands of people that are. If you plan on not giving away your comics, well, selling at conventions without people knowing about your product is just as hard because people don't like to take risks with their money on stuff they don't know about.
My passion is making comics but I think I'm going to switch over to just fine art painting. I've been doing comics for about 4 years now I've made about $–3000. This 1.5 years in fine arts grad school I've made $8000. fine arts painting is also way easier than making comics as well and the people that have money to buy fine arts are loaded with cash. I'd rather make art for them than people complaining that my 120 page, full color, graphic novel is too expensive at $15.