What is the issue here? The downside of Reckless Attack is that the barbarian also gets advantage against them. This is why it is a reaction to attacking, and why it enables ask by default. You can still miss with the reckless attack roll.
Advantage means you take the best of the 2 rolls. He shouldn't have been able to end up with a worse result, yet he did. That's the issue.
They'd already rolled once and missed, so using Reckless Attack for "advantage" in this case actually means making a second roll. The second roll was also a miss, so they still missed. This is the correct behaviour.
The only thing incorrect about this is that in 5e you have to declare Reckless Attack in advance, you don't get to wait until you miss; Baldur's Gate 3 is a lot more permissive in that respect, though I guess it's costing your reaction so it's probably not too powerful.
