From the perspective of a person here who knew about DC and marvel comic books, yet never really read most of them. Nothing which some of you guys are talking about like flashpoint actually registers high on any of the non-comic book fan's conscience. You have have to be a DC comic book fan to know about flashpoint, but I will bet that the number of potential superhero movie goers is far more than the number of comic book fans.
This is why I feel that they just have to make good movies. Its not about killing yourself trying to create a coherent universe (though that helps abit). Its about making a good movie and telling a good story.
Too many superhero movies are relying on an origin story, and how the superhero beats some CGI heavy big baddie to tell the story. Its overused and rehashed to be point where its no longer a draw anymore. If you are introducing a lessor known superhero that the non comic book fans don't know about, then their origin story has to be interesting enough on its own. It can't be the only selling point. Meanwhile, the known heroes origin stories are already well known. How many times do you want to rehash how batman or superman came about ?
So, tell a good story and make a good movie. It doesn't need to be so closely linked to the DCEU at all. Look at how successful the movie Black Panther was, and yet, it didn't really have any mention or link to the Marvel universe at all. It would have made all the money it did even if it was a standalone. And for all respects and purposes, it was a standalone movie.