Is it putting the fins ON or taking them OFF that's a problem, or both?
I put my fins ON by lying back in the water and doing the figure 4 in front of me, when I'm shore diving. It's WAY easier than trying to reach my feet while standing. On a boat, I'll either get the crew to help me, or I'll do the figure 4 while standing and holding onto something, but either way, I make sure I have the suit full of air, so it's maximally loose and flexible while I'm coping with my feet.
Shore diving, you stand in deep water to doff fins, and the suit collapses around you and makes it hard to move. Closing the valve and pumping a little air in will make the process way easier.
It's easy to underestimate the amount of restriction caused by even a small amount of dry suit squeeze.