i have a lot of perennial phlox (the tall kind that blooms all summer)
in my shade garden. would it be happier somewhere sunnier or should i
just leave it alone?

Depends on the phlox, as I understand it. We have some sun phlox and
some shade phlox, and my books list quite a few kinds (both species
and cultivars). Since you have a lot, maybe try a few plants and see
how they do?