Barrelmancy is "ok" in Divinity OS 2 because it follows whatever logic Larian studio wants.

But it doesn't merge with Baldur's Gate franchise, and doesn't make sense in DnD 5.

Let's pretend that the common barrels we see in the game (firewine barrel) weights the same as wine barrels do in real life.

Empty, they weight around 90 pounds, and full they weight around 600 pounds.

In the game these common usual barrels weight 10 pounds.

And the "That's no big deal, because players don't have to use them if they don't want to" is the kind of excuse that can be used to implement whatever flaws in gameplay, lore, or mechanic:

- How about putting infinite attribute points at player's disposal on character creation?
A: "That's no big deal, because players don't have to use it if they don't want to."

- How about a portal opening on player's camp, and having a demon giving explosives with no weight and automatic crossbows, so everyone can cheese the game more?
A: "That's no big deal, because players don't have to use them if they don't want to."

- How about putting all magic scrolls inside an infinite bag of holding on the beach, so the player can access all of them on the beggining of the game?
A: "That's no big deal, because players don't have to use them if they don't don't want to."

And the list could go on for a series of absurd things, that could easily be defended using this same flawed logic.