Anything contrarian to the norm, when coached well, will be difficult to handle. As time goes on any system requires innovation because defensive systems and coordinators get accustomed to dealing with it.
Just look at the typical DEHS coverages rolled out today- lots of teams base out of a 2-high safety look. 10 years ago you may have seen 1-2 teams a year...everyone else ran some version of 1-high safety (Cover 1/3) or no safety cover 0. It's because many offenses today employ some version of 1 back offense and force teams to cover 4 vertical receivers immediately at the snap. If you don't have the flexibility to deal with the different offenses you see you're dead in the water.
Remember not to long ago the 3-3/3-5 odd stack defense was all the rage. It was a system designed to deal with spread teams. So offenses went back to running power off-tackle stuff and defenses have to adjust. Hence the quick death of the 3-3 stack.
The okie 5-2 was designed specifically to deal with the wishbone offenses of the 70's. Now that nobody runs it the okie 5-2 has died out. That defense has a hard time aligning and playing assignments vs 1 back offenses.
It's all cyclic.
But as others have said- I would LOVE to see some double slot navy-style flexbone option stuff in our area. But running a few plays of this offense and a few plays of another etc is just a garbage offense. They need to be "all in." If they do it, if they go all in and coach the mess out of it, they might be able to see some success that lining up in an I formation with an average tailback won't get you.