You have it backwards in a common way: knuckle armour is the least important part and the palm is the most.
In a fall, hands go out. What contacts the road is the palm and the outside edge of the hand, at speed, and what happens next is abrasion and then the hand catching and twisting. Knuckles hit things occasionally; palms hit the road nearly every time.
So what actually matters, in order:
Palm abrasion resistance and reinforcement. A double layer of leather across the palm and the heel of the hand.
A slider or a smooth reinforced patch on the heel of the palm. This is the piece that lets the hand skid rather than grip and twist, and twisting is where wrist and scaphoid injuries come from. It is the single feature I would not buy without and it is absent from most cheap gloves.
A wrist closure that keeps the glove on. A glove that comes off during a slide has done nothing. Anything without a proper wrist retention strap is decorative.
Coverage past the wrist bone.
Stitching and seam placement, internal or protected seams, because exposed stitching abrades first and then the glove opens.
Knuckle armour, genuinely useful and last on this list.