It’s an okay piece of equipment. It’s not a miracle machine and is not the best thing since sliced bread. If you want to use it, or if you enjoy using it, then that’s fine. You don’t need a huge range of motion on it.
I wouldn’t only use this machine as your single core exercise. More important is being able to brace your core under heavy load and have the ability to brace your core during all exercises, such as pull-ups, pulldowns, squats, deadlifts, and overhead presses. It’s one thing to be able to feel your abs while sitting in place on this machine, but are you able to feel your abs working during bigger movements, such as squats and jumping? If you can only feel your abs sitting on this machine, then that’s no good. I’m not a big fan of doing an entire workout sitting on machines. I notice a lot of fat people sit while at the gym. Seems to me that if they just come to the gym to sit and lift light weights, they might as well just stay home, sit on their sofa, march their feet in place, and lift some carpenter pencils overhead.
Yes, many fat people use this machine at my gym too. But so do many in shape folks as well. A lot of fat people eat pizza and burgers. But so do a lot of fit folks.