We just had a Marvin exterior door installed with compression weather stripping and it is impossible to open. Although the one upstairs works fine, everyone says this downstairs one is how it is supposed to be and that we'll be grateful in the winter. In the meantime, no one of any age and size can open it without a huge struggle.

"We just had a Marvin exterior door installed with compression weather stripping and it is impossible to open. Although the one upstairs works fine, everyone says this downstairs one is how it is supposed to be and that we'll be grateful in the winter. In the meantime, no one of any age and size can open it without a huge struggle."
If this is the case, the door was improperly installed. It could be a simple fix by either adjusting the door strike or installing an actual adjustable strike mechanism in place of the one you have.
Ron