"Hero" is a title thats bestowed by the people after the person does something heroic. It is not about strength, but actions.
When it is bestowed before said action, then it becomes a job title, no different than a farmer, no more, or less, amazing.
A chad like Himmel in Frieren deserves the title of Hero because of what he did, not because he was strong. And, as expected, he was never called a Hero before he took action. Whereas all these isekai cheat 'heroes' got their title before they even started the journey. Its a title saying they had power, not that they are heroic. Its a common difference.