What I love about Danmachi is that Bell is rarely the strongest person around, and unless he has a really good strategy to beat his opponent that's several levels above, he just doesn't.
Loss is an important step towards success and many LN forget that process and just jump straight to immediate success in rapid succession (especially isekai ones).
That's why I love both Danmachi and the Toaru series, they're similar in that the characters are constantly making mistakes or wrong choices trying to figure out the best solution to the situations they're in, eventually changing sides as they learn more about the world and themselves before they can finally grasp that win after much sacrifice.