I dunno, I like to think that I do subscribe to minimalist collection theory, and it's very enjoyable. I actually
purposely reduced my collection of 31 different types of guns down to 4-5 basic types, with copies of each for backups of course.
The entire reason behind it was because it was aggravating most of the time trying keep proficient with everything I had. Just as I'd reintroduce one firearm to myself and get better (note I did not say "good") with it, I would pick up another rifle/pistol/shotgun for a few range sessions only to find that, not only did I suck with the firearm I just picked up, but that I would totally eventually lose proficiency with the last firearm I tried to reintroduce myself to.
It was a viscious cycle of bad days at the range and good days at the range. I found I questioned my ability - a lot.
Some would say it's boring not to own/shoot many types of firearms. Well, that may betrue for some, but I find nothing boring about leaving ragged aiming circles behind after every range session, instead of every other.
It still doesn't have to mean a "small" collection to be the minimalist. Even with only 4 calibers, I have 14 guns now. 4 1911's, 2 FAL's, 2 870's, 3 22LR rifles, 1 22LR pistol, and my mismatched pair of utilitarian rifles - my 22 Hornet and my 22mag, the two latter being the guns I grab in those times when meat needs to be on the table that night (every once in awhile, my pocket lint seems to devour my paycheck, and certain things are necessary to keep the family fed
).
I'd like to get rid of the 22lr rifles, but I try to keep'm around for when the kids or the wife want to go huntin with me. Not to mention, quality-wise, they are just downright unsaleable. 2 of the 45's are nothing but toys. I do plan to eventually rid myself of those guns in the near future, but only in the form of gifts to close family.
Nothing wrong with being a minimalist, but it does take a certain mindset to accomplish. I got rid of some sweet guns to get here, guns I thought I might regret selling later, but that has not been the case.