I can understand where directors who are used to more or less having free rein to do whatever they want might have a problem with the MCU approach, but I think a more hands on approach by the people in charge of the universe makes sense when you're movies are as connected as these cinematic universes are.
Which is exactly why I liked it that the DCEU from Aquaman onward has barely been connected at all, with each film free to be its own entity with its own tone and approach, just sharing the general background. Its strength was that it wasn't just a copy of the MCU's approach, but an alternative to it, a looser, more anthology-like take on the shared-universe idea. And that's why I'm sad that the new approach is to scuttle that in favor of Yet Another MCU Copy, a strategy that has failed miserably for almost every studio that's tried it, including the early DCEU.
It is free rein right, as in letting up on the reins so the horse has more freedom to movie? Or is it free reign, as in a ruler having the freedom to rule how they want?
The former, yes. The full expression is "to give free rein," to grant the horse more freedom of movement. Nobody gives someone reign; you're either born with it or you take it for yourself.