The armor of the man-at-arms on the field of battle has the purpose to function.
The armor of the man-at-arms in fiction has the purpose to look cool.

>I want the armor of the man-at-arms in fiction to look functional
it's like eating soup with a fork, it's like using a pike for dueling, it's like using a Frog-mouth helm for infantry.

You're acting like a child, trying to fit a square peg in a round hole, and the study of warfare and equipment should have taught you the opposite: every tool has a function.

The tool made to work in the real world is not the right tool to work in fantasy artwork.
Like a gas mask on a Roman soldier or a rectangular sail on a transoceanic ship, like a bright red uniform in WWII, your idea makes no sense. Wrong tool for the job.

As you see, the weapon on the left is a perfectly functional fantasy sword, perfect for appearing in artwork, showing personality, and signifying power to a large quantity of people.

The weapon on the right is a flawed fantasy sword, it is truly gimped in its usage in fantasy artwork, relegated to a niche of very specific gritty or low-stakes scenarios.

As for all tools and weapons, it's all about functionality.