@ezra sand is undoubtedly not a problem, where it falls apart for me is the gunpowder cause I need 2 or 3 creepers' worth of that for one TNT block, and in the time it'd take me to get the materials I could just manually break 10 times the amount of blocks that would be blown up
admittedly I have never thought about TNT dupers even though I've seen them a couple times on yt, but in terms of purely intended mechanics TNT just feels super pricey for what you get out of it in mining