Of late, I've started to study swords and HEMA. This has given me a half decent knowledge about swords. But this has lead me to realise just how many bad swords there are in miniatures. And the ancient and especially medieval periods suffer from this. With many swords basically looking like oversized aluminium bats with a crossguard.
The later periods does seem to suffer less from this, even if the swords aren't perfect recreations, they are slimmer and look like swords.
I'm not naming or shaming, but I looked at some reinesance Spanish rodeleros.
The sword looked like aluminium bats versions of a 12th century knightly sword.
Besides the oversized part, it had very high medieval crossguards. While some illustrations show a straight crossguard.
It's more common to show them with sideswords that have complex hilts.
But even if you ignore the hilt, which as I said some does show them with straight crossguards. The sword is still oversized and completely the wrong shape, late medieval arming swords(which these would be) would be extremely tappered and ending in a very fine point. Not batshaped at all.
I have seen medieval miniature with excellently made swords. So it not a "have to make them like that because of the metal" thing.