You're basically rehashing my point by saying they're developing their own corner. The films don't acknowledge them (never have) and the TV shows are no longer boasting the "it's all connected" theme and haven't since CA:TWS. The fact that they are owned by the same company is a technicality.
Sorry, I was confused when you said "separate" universe as if it's no longer canonical. And films don't reference the shows for two main reasons:
1. The narrative doesn't call for it - as in throughout the film the characters have no reason to mention or reference something other than a wink, wink nudge, nudge to the fan base. If it doesn't serve the story it's just excess fat. Take for example Civil War an how they don't mention Inhumans, that because maybe not all of the audience have seen AoS and would have no idea, but more importantly it does nothing to develop the characters themselves. When discussing the accords they only talk about how it affects them because it is essential to the plot of that movie. They're not going to waste time in this high budget film already filmed with tons of characters and subplots discussing parts of the accords that are irrelevant to the story at hand. Also since winter soldier Shield has operated as an unsanctioned, off the books, privatize, black ops organization. No wonder they're not mentioned very often.
2. Films are prepared and filmed way in advance - as opposed to television which has a farther quicker development cycle. It's far too difficult and unreasonable for film directors to keep tabs where they're already concerned with massive films. To put in perspective. AoS started writing season 3 with in a few weeks of when Civil War starting to film. The Russo's did not have any idea what exactly would occur in AoS as the writers were just figuring out. So the burden of connectivity is an always have been placed on the shows. No secret that the films take the lead, not follow it. You could come up with your own head-canon where they discuss Shield, Defenders, and whatever else of screen, because it's not relevant to the story at hand.
Also I have a huge pet peeve with people bringing up the "it's all connected" line from early interviews. Being connected doesn't mean it's part of one grand narrative, simply they take place in the same universe. They never said it's building to some kind of a grand crossover, simply that it's connected. It's canonical. And the reason they don't say that often anymore is because they don't have to. When the show started there were a lot of questions of what it would be and they want to make sure people knew it was part of the universe. Being the first tv show as part of the MCU that's an important point to make sure the potential new audience understands. Now people know it. Iron Fist doesn't need a line about an "Iron suit or magic hammer" in the trailer to indicate to an audience it's apart of the MCU. People get it more now.
Tv character may never show up in the films, but I doubt that because of some rift between perlmutter and Fiege or that they're not somehow canonical, but rather because the story doesn't call for it and probably some logistics with scheduling/contracts/etc can be in the way.
