Here's my take on it: I much prefer .38 Special, .357 Mag, .45 Colt, .44 Special and Mag. But, I have a three screw .357 Blackhawk with an additional cylinder for 9mm. I can load it with a home-cast 125 grain flat nose bullet using homemade bullet lube and a small amount of shotgun powder. I generally load it to a very useful power level, in the range of 800-1000 fps. And the brass is free. It is not uncommon for me to pick up 9mm brass until I am tired of picking it up, when I stop at a shooting area during a motorcycle ride. I have a decent amount of .38 brass, but using the 9mm brass allows me to conserve my .38 brass for my better loads.
As for ARs, I like them. I also like lever actions, bolt actions and single shots. Front stuffers too. One does not preclude the other. I am a tinkerer, and the AR is a tinkerer's dream. As for 5.56/.223, I completely disagree about it being a worthless round. I like the .222 round more, but it lacks one quality the 5.56 has: free brass. See above comments about 9mm. I cast bullets for it, too. A 55 grain cast bullet conserves my lead supply, and pretty much any powder I have can give me a useful power level especially if I manually cycle the action (which also makes it easier to save my brass). From standard velocity/subsonic .22 LR power to .22 Magnum and beyond. That, to me, is a more useful power level than full power .30-06, for example.
And then there is .300 Blackout. You can make brass by cutting down some of that free 5.56 brass. I think of it as .32-20 for ARs, but with free brass.