There are plenty of accessories, just like with lifting. Maybe my main lift is the dead lift and after that I do some Romanian variations, rack pulls, reverse's , whatever. Sure , that's cool, that helps, it gives me volume and variety, but if all I do is the accessory work and never hit my main lift, never perfect that form, never push it? I've heard it said not to "major in the minors".
I've been pulled that same way shooting too. There's a challenging test or drill and I would shoot it over and over and over until I could rock some real impressive score, and sure it helped my shooting some and got me some trigger time, but the kick ass score on that one drill wouldn't translate to every expression of the foundation. Shooting one classifier until I can shoot it at Master level doesn't turn in a Master level match performance.
And so it is with "this thing of ours" , there is no good enough. There is no if your a B class uspsa shooter, a blue belt in bjj, and can squat your body weight for reps you automagically can use those skills or better yet combine them under duress in a chaotic and ambiguous real time event.
But here's the crux of the thing. If we want to be able to be multidisciplinary, we do need to have multiple disciplines we can base off of first! You cannot work application with no delivery system, and the foundation must be strong, stronger than whats needed in application I believe, as base skills will degrade under ever increasing layers of complexity.
Punch a Black Belt in the face he becomes a Brown Belt. Punch him again, a Purple...
-Carlson Gracie Sr.
So how much is good enough? I don't think that matters. Good enough for what? We cant predict precisely what our needs might be. We might be able to make some generalizations of risk profile based on profession and environment, but beyond that, esp for the armed citizen, sometimes just being aware and willing are enough, and sometimes the boogeyman comes knocking.
I stay hungry, I'm always pushing for more. Why? Its not cause I'm concerned about the boogeyman, it's not because I don't feel I'm "good enough" or any other sort of insecurity and fear. No. I keep at it because I keep getting better. Because this puzzle is deep and fights you back. Because I'm a better person for it. And because the better I get at understanding the paradigm the more able I am to help you down that path and be a part of good people taking self ownership, finding confidence, and overcoming adversity.
If you want to walk that path you know where to find me.