Theres been many suggestions lately that are a attempt to address this.
Personally I think if you have the right thing equipped onto your back, when you try to do the function it should automatically use it from your back slot since we have slots clearly marked for knives, axes and pickaxes, yet, equipping into these slots offers zero function in game, as if putting them in the correct slot doesn't matter and won't let you use it.
I do agree tho it would be pretty simple to just let people keep things in left hand, while keeping in right.
But the "confusion" for most new players comes when the weapon says it needs to be in the right hand, but says nothing about keeping your left hand clear, so almost every new player I know of asks about this and I need to tell them to take their left off..... this isn't great.
So the message needs to change to include taking your left weapon off OR a major change needs to happen to how skills use equipped weapons.
One last thing to note is that for example, having to equip only a knife in your right hand while hunting can leave you open for attack since you would need to than re-equip your main weapon in order to fight back, giving the attacker a few free hits with the new fast attack mechanic.. this seems unbalanced, so I really feel like there needs to be a system of using the back slots to use skills instead of equipped slots.