It's not even about Batman or well established franchises. It's about IPs and ideas in general. Just try and think of how many new characters, concepts, franchises, etc, were created in the last 20 years and how many of them were actually worth a damn. There's Halo, which 343 run into the ground. There's PotC, which Disney run into the ground. There's Mass Effect, which Bioware run into the ground. There's Hellboy (created in the 90s, but you get my point), which Mignola run into the ground (not on the level of the previously mentioned franchises but still). Jak & Daxter, Ratchet & Clank, Sly Cooper; all dead. Uncharted is an example of keeping up its quality, and froom animated shows the Venture Bros. You get where I'm going with this. New ideas are hard to come by, yes, but if you care enough you can craft something good even if pre-existing IPs follow the same beats. The problem is that these days nobody cares. They put out **** and the consooooomers consooooom because that's all they can do. Fill their days with meaningless ********, move on to the next and pretend that it's alright. How do you think Netflix still keeps making all their trash?
The reason why the older stuff are generally better than the newer stuff is because either they were there first and already covered all the bases of a concept, or because they were crafted with love. The first Halo Trilogy, alongside the spin-offs, the toys, the comics, it had soul. The new ones are nothing but cashgrabs. The early Ultimate Marvel was an experiment that managed to capture the zeitgeist, but as time went one it devolved into a horrifying mess. WildStorm was more or less the same. And the problem is that ultimately, it's all a business. Something starts off as small, and niche. It has a specific flair and appeals to a certain demographic. But then it gets more attention. And more. And suddenly the creators want to make more dough, so they forego the things that made the property special, and try to make it as inclusive to as many demographics as possible, so that more people will get into it and buy it. And thus they fall backwards to appease the newcomers who cannot, or won't, dwelve into the "esoteric" nature of the property. And so it gets dumbed down. And slowly it changes. And ultimately it transforms into something unrecognizable. The old fans, the actual ones, have moved on, they have been kicked out. The newcomers? They've already moved on to the next shiny new thing. And the property? Only its battered and mangled corpse remains.