Oil filter seals aren't any softer than o-rings, and by the time they get changed, they've usually hardened up even more.

You do get o-rings made from softer material, but they're not common place.
I wonder what the proper name for the seal strip type stuff that comes in strips and used for sealing junction box covers is called. I've worked on various junction boxes, where the seal is just a press fit into a machined groove. It's usually a round or rectangular shape, and is normally very soft so you get a good seal with minimal pressure.