Whether removing copyright would lead to more "milking of same old topics" in movies. I think the answer is self-evidently yes.
This is not self-evident to me, at least as far as "milking" goes. Inspiration is not the same as milking. I specifically use the word "milking" for the sort of low-level repetitive quasi-effort that the cinemas are full of.
OTOH if someone takes, IDK, Don Quijote and rewrites it into a space opera, it might actually be genuine fun, even though the old idea was there as a foundation.
I don’t see how it would lead to a higher volume of original ideas.