I somewhat agree with you. My next build is going to be an AR-10. I have a .30-06 hunting rifle and a .303 Lee-Enfield that will suffice for the time being. But one of the nice things about the AR-15 platform is reloading wicked fragmenting rounds. It is difficult to get the velocity up on a 180 gr. 7.62 round to make it fragment. You can get knock down power and expansion with 7.62. With all the body armor around these days, you need to think "hips and head" when targeting. Hips are full of arteries that are just waiting for fragmenting rounds. It immobilizes the target with a quick bleed out. I'm not saying that similar or better results can't be achieved with different targeting using a .308. I would say, I would rather have knock down power if a drug crazed target was rapidly advancing on me.
30-06 is my favorite cartridge, but almost all 30 caliber cartridges can be loaded to be very effective.
I have a bullet mold that I bought for my 30-30 Winchester (170gr FP) that will work in a pinch in 308 and 30-06. After 2000 fps leading might be an issue depending on the barrel.
But the same can be said for a lot of pistol bullets. Most people do not know that 9MM, 380, 38, 357 all shoot the same diameter (lead) bullet. Some bullet molds will work in all 4 (not ideal for all).
When reloading supplies are low, as they are now, you can always improvise.