they didn't really iterate on Souls formula, the series is full of great features/QOL improvements that were dropped for absolutely no reason.
They didn't iterate on everything, I agree, but we can clearly see attempts to improve or change the formula with each subsequent "Soulslike" (and really, someone needs to come up with a better name for these games, it's the "Doom clone" shit all over again).
I don't think there's any From game that has worse and dumber amount of large open maps filled with shit not even worth dealing with as DS3 did with Road of Sacrifice, Farron Keep etc)
With From it's like playing roulette, you never know what you'll end up with from game to game, or from level to level even. DeS had quite a few good levels, but a bunch of really shitty ones, DS1 starts out great but the further along you go you start recognizing the places where they had to rush things and cut corners, ditto for DS2 where the base game is mostly a disaster while the DLC are pretty good.
It seems it's less of an issue of skill, since they know the principles of encounter designs, and more a lack of time to polish or even design these encounters due to the development schedule.
They've actually devoted twice more development time to Elden Ring than to any previous Souls game so I'm hopeful they had the time and resources to do a proper job with designing the levels. Then again, the amount of content they're packing into the game might very well have led to From stretching themselves too thin.
On the other hand, what I'm actually worried about is the open-world and how they are going to handle encounter designs there, and if they will be able to make the overworld feel meaningful and interesting to explore, or if it will degenerate into another shitfest of grinding for resources and following quest markers from one point of interest to the next until you've crossed them off the checklist.
Then again, there's no quest compass, so at the very least they want the player to properly experience the world.