Other methods may be obsolete in the pure target shooting and competition arena with a few exceptions but as with most things that work great under controlled conditions, it can, should, and has to be modified to fit your exact situation at any given time in a defensive scenario.
For example, are you going to be thinking about your thumbs forward grip that you trained so hard to perfect when you need to shoot now and you have sustained a serious shoulder injury?
It’s all a matter of perspective.
It is all a matter of perspective, and perspective is often just what you know.
When the next latest and greatest shows up, everything else is obsolete, or, at least so youre told. Is it always true? No, but it could be.
I think no matter what youre using in the moment, you need to at least give the latest and greatest a good try, and see why it is what its supposed to be, or how will you ever know? Maybe it is, maybe it isnt.
Things progress as time goes on and better ways are always figured out. Some go easily along with that, some need to be dragged, kicking and screaming into the current truth.
The big advantage to those who have learned the "obsolete stuff" and yet continued to progress all along, they have the knowledge of all that they learned in the past, and have that to draw on when things arent perfect and might require some adaptation.
I see that more with "stances" than I do "grips". These days, I have two grips. One handed, and thumbs forward. Thumbs forward, simply because Ive found, that for right now anyway, its the best grip for me.
Stances, on the other hand, are what they are in the moment, and just morph into whats needed as Im shooting. Might be one handed shooting one way, some sort of modified Weaver as I do something else, some sort of Isosceles if everything is right in front of me, etc.
I draw on all of those "old and obsolete" methods I learned in the past whenever I need them. I havent discarded any of them, just stored them away for when they might be needed, and what works best. My brain seems to know what and when that is, so I dont worry on it.
Im also a Bruce Lee fan when it comes to anything, and shooting is no different. Learn as much as you can about as much as you can, and take from that, the best parts of each, thats most useful to you. That has always worked very well for me, with pretty much everything.