I still use high power ND filters and CPL. But I do not use a big plate system anymore, nor graduated or any of those ND filters. Too much cost for a bunch of stuff to carry around, stack, fool with. I sold it all. I just use a simple set of circular ND filters (10 stop primarily) and a CPL (when I want the CPL, mostly for reflective water surface). I do 8+ minute exposures with this using different techniques of median stacking to achieve the same look, without the negative effects of stacking a bunch of filters, the sensor heat and noise of a true 8+ minute singular exposure, and the problems that happen during all that time frame if something moves, vibrates, random stuff, etc. So I'm more in the digital camp with this now too, but I still use a few ND filters to get there. I generally don't recommend the big plate filter systems anymore, they're expensive and cumbersome and have their own issues and the end result can be done without them now.
Very best,