The point of dynamic optimizations (such as ooo) is not only to hide implementation details (such as register file size) but very much to take advantage of dynamic opportunities that simply cannot be known statically. The optimal schedule can be very different depending on whether some load hit L1 vs L2 or even was forwarded from the store buffer.

There are some classes of very regular algorithm where you could probably predict everything (and handle the memory hierarchy) statically, such as GEMM, but it's not very common.