You're fundamentally not understanding the role of the 47mm or 75mm AT gun in the French army. A heavy AT gun which is placed in the rear and deployed to protect the artillery and to provide mobile reserves ISN'T something which is shooting at soft targets - it is deployed specifically for the purpose of stopping enemy tank offensives. The Germans got use of their flak 88s in shooting at bunkers and hardened targets, but the Germans were on the offensive and needed to move quickly under their doctrine - the French had no such problems since their integral fire support came from their attached tank forces for infantry divisions and their massive quantities of heavy artillery and their offensives were by design slow and reliant on massive artillery fire to suppress and destroy obstacles rather than using direct fire weapons. The capability of shooting at infantry targets is not important for the 47mm or 75mm gun in the French army - it probably would have made sense with the 25mm guns, but not the heavy AT guns, it is like designing your main field gun around being able to shoot at air targets - the costs to get that performance far outweigh the actual benefit you get from it. Having a good anti-tank is what mattered, and the French found that the 75mm was not a good anti-tank gun, which is why they developed the 47mm instead.The mle.1931 has .313 pounds of HE for a burster, and the 47mm mle.1937 cannon weighed 2500 pounds.
The mle.1916 AL HE had 1.63 pounds for the burster. You need Five 47mm shells to have the effect of the 75mm explosive round.
The French mle1918 APHE had .2 pounds for the burster after penetrating 61mm of armor at 500m
They also had a variety of other semi-ap rounds with up to .72 pounds of HE with penetration up to 40mm for wrecking lightly armored targets.
Yes, the mle1897/33 weighed 800 pounds more than the 47mm, but had more capability than just drilling holes and tossing a high speed grenade, like smoke, cannister and shrapnel