I think the obvious answer to what everyone keeps asking is that MC could absolutely be a good swordsman. He just can't impress people who don't value HIS style of swordsmanship, which would likely lean toward a more delicate/precise style rather than raw strength. In a way, it's like all those other stories where a magic family only loves their fire mages and hates the talented wind mage despite being an absolute prodigy.
Beyond bashing the 'muscles!' mindset, it also seems to be taking a swing at the 'might is right' mindset as a whole, including from the mages.
Edit: I think it's also pretty clear we're going to see SOME of the 'magic? swords? why not BOTH!' tropes. "we never thought about combining the two to train a magic swordsman!"