There are a number of firearm & cartridge combinations which fill the same niche - 44mag, 454casull, and 45-70 leverguns, 454casull and 460S&W revolvers and specialty pistols, 458 socom, 450 Bushmaster, and 50 Beowulf AR-15’s... They’re a lot of fun to shoot a little, and they anchor game quickly with minimal meat damage at shorter ranges, which is advantageous in thick brush.
I have or have had most cartridges available in the AR-15 platform, including 458, 450, and the 50. Out of the 3, I go back to the 458 socom (unless I were hunting in a straightwall only state).
It is true, however, the 6-7mm cartridges get far more utility from the AR-15 platform. The 6.8 spc, 6.5 Grendel, 243LBC, 7 Valkyrie, and their ilk really do maximize the in-field potential of the AR-15. When hunting, I grab a 6.5 Grendel or 6.8spc to do work, and only grab a 458socom for the novelty.