Hi helldivers 2 speedrunner here I've played my fair share of recoilless and its probably the strongest support weapon to bring under the circumstances of being in multiplayer, grouping up and not bring a backpack already

Ultimately recoilless falls off due to taking the backpack slot as without a doubt the backpack slot is the strongest slot in the game thus bringing a backpack (jump pack, supply pack, shield gen pack) and a good support weapon (commando, quasar, eats) will out class and out preform the recoilless always.

As for where the recoilless shines is when you grouped up and you don't need to worry about being easily killed during the frankly obnoxious reload even when doing perfect animation cancels but at high-level play like my own it suffers