We have made some advances in man portable arms available to the infantry squad since WWII, I'd say chief among them being things like the M203 and light and medium machine guns like the M249 and Mk48.
I'd say the biggest advances would be all the on call support to the infantry squad, the improvements in communications, GPS, etc. They didn't have SATCOM, FBCB2, GPS navigation, BFTs, and all the other wonders of modern communications that make it easier for the squad to stay in contact with HQs, ISR, CAS, etc. back then.
Oh yeah, and they didn't have body armor or speedy medevacs like we do now, those have saved a lot of lives.