What have people liked more? The mess of the prior DC movies, or, Joker and the Batman stand alone films, which are both slated for and one sequel that's now filming. What if the new DC direction is to move away from prior established style and move onto that gritty real world style?
Wash the slate clean and make something with the investment.
Again, it seems like they're putting the cart before the horse those. The now dead DCEU was done (literally from the head of DC at the time) to cash in on the success of Marvel and the Avengers. They jumped right to BvS and nosedived from there (can you really nosedive from such a low spot?). This time, again, they're simply assuming success based on the fact they're DC and plotting out 10 years of stuff before a single scene has been shot. Now, maybe studio's plan things out that far - but they don't do it publicly. I expect next years DC Con or whatever they call it will be Gunn and company doing a Marvel style presentation announcing 9 flicks over a 3-4 year span.
They should be fully aware at this point you have to earn it. Gunn especially. He was tasked with making Guardians not just successful, but getting people to buy into a stable of characters most (and i mean 95% of the movie going public) had never heard of that including a talking raccoon and tree. He knocked it out of the park. And sure, it wasn't just him, but they had to go through all that while having a successful slate of films. Loads saw that simply because Marvel had a great track record at that time. With all that, I think he's got a much tougher gig with the first new DC flick. You've got a studio most people think of as a joke who can't get out of their own way who's just ended all the existing characters and now they're making public plans for 10 years of 'universe' movies. It doesn't sound like they've learned a whole lot quite honestly.
I get Gunn has a better track record and has been on the successful side. You've still got Mr Discovery Channel calling the shots overall which is a scary thought. Maybe they need that 10 year plan, but they'd be a whole lot better served starting from square one and only talking about the next movie and not 10 years worth of universe flicks.
I heard before, who knows if it's still the plan, that Joker would stay in it's own world and it was unknown if Battinson would be the batman going forward or if they'd redo that. That joker is no criminal mastermind and would get smacked down by any batman in about 30 seconds. It's good using it as a story about mental illness, but I don't see it translating to an actually viable batman villain. The guy is mentally ill, not a criminal mastermind. As for gritty, look at most cities, you have nice clean parts, suburban parts, and gritty parts. There are some pretty seedy cities out there as well. I don't have a problem with Gotham being gritty and Metropolis being prim and proper etc. That can work. DC's past mistake was that everything wasn't gritty, it was all dark, depressing, and moody and used more green screens than a stone George Lucas. I don't think all DC flicks combined had 10 minutes of footage with a bright blue sky. It was just visually dark and depressing and that is not what super heroes are. Batman, for example, may do most of his work at night in the dark, but Bruce Wayne should be out and about during the day when there's sunlight. You need that grounding in reality which the prior DCEU seemed to have skipped completely.