If one hacked the ROM to eliminate the "Start Mission" option on launch, that alone would make Final Frontier much harder to get to. I can't actually think of another game that has a wizard mode that can be started on a plunge.
Aside from that, TNG was ahead of its time as far as depth goes. And while it's not that hard to get FF, you are compelled to take shots in modes and get the artifacts to make FF meaningful, rather than just timing most/all of them out to get to the wizard mode (like ToM). And of course when you shoot you risk draining.
At least worth an honorable mention is RBIoN. There's a lot of ways to get the Ripley letters and start the wizard mode, but it's not easy.