It's a shame that dual wield is already pretty useless in the dnd 5e vanilla, but the way it is programmed in the game brings even more hindrance to an already kinda useless flavorful trait.
What I noticed is that early on the early access all offhand attacks had the ability modifier added to damage and not to attack. Newer versions partially corrected it, getting rid of the ability modifier to damage unless you have the fighting style for dual wielding. But, the attack modifiers is still screwed up.

Basically how it should be:
- IF you're proficient with the weapon, you add the proficiency bonus AND the ability modifier to the ATTACK ROLLS in both hands IF both the weapons are light.
- IF you have the fighting style for dual wielding, you also add the attribute modifier to the DAMAGE ROLL for the OFFHAND ATTACK (the main hand attacks always have the attribute modifier to damage unless specified otherwise by another factor).
- You CAN dual wield non-light one handed weapons IF you have the dual wielding FEAT, which also gives you +1 CA while dual wielding and let you draw two weapons as a free action instead of one.
- Hand crossbows need both the dual wielding feat and the crossbow expert feat to be successfully dual wielded because of the loading quality.
!!!!! - Offhand attacks are still attacks should be allowed to be combines with other abilities, such as rogue sneak attack, fighter maneuvers, paladin smites. This is super important, especially in the setting of you guys from Larian trying to increase usefulness and flavor of melee classes (I remember Sven talking about this in the last panel from hell). !!!!!!

I really hope someone from Larian take a look at this and anyone please do feel free to reach out if there is any disagreement or interest in discuss possible improvements.

Hugs and love all around,
Stay safe y'all.