They are doing the online subscription thing. You can buy a monthly subscription to Marvel Unlimited or DC Universe and get access to every issue, albeit 6 months after the dead tree version is published, as well as a huge catalog of back issues that gets continually expanded. Marvel and DC both plan to eventually have all of their back catalogs available digitally. DC, as part of a makeover of DC Universe after it looses the streaming video element, will also be publishing exclusive online content that won’t have a dead tree version.
There are also services like Comixology that allow you to subscribe to various titles online, and a lot of content from a lot of publishers is available for one-off purchase, directly from publishers, through third-party specialist services like Comixology, and through Amazon.
Publishers are desperately trying to figure out how to survive in the new media ecology. Some individual webcomics are thriving. Some individual creators are doing fairly well as independents using “non-traditional” funding and publishing venues like Kickstarter and Patreon. But “mainstream” super hero comics are struggling, and have been for a couple of decades now.
I personally love “mainstream” super-hero comics. But kids these days, with their tick tocks and their instantgrams and their hair and their music just don’t seem particularly interested in those stories and those formats, whether presented digitally or on paper.
I think super-hero comics as a genre will survive, but we’re heading into something akin to the pre-Code era, where supers were just one of a large number of genres, and a fairly minor one at that.
Oh, and as to Gerry Conway’s solution, both Marvel and DC have tried that. Repeatedly. Marvel, in particular, has launched umpteen different “all-ages” lines with self-contained stories, going back to the 1980s. They all folded, because they simply didn’t appeal to the kids that they were supposed to appeal to, and the adults who are the audience that actually buy and comics nowadays (“nowadays” going all the way back to the 1980s) didn’t like them.