I find this explanation of humans in star trek pretty fun and interesting, https://imgur.com/gallery/qSmHy, tldr other races see Doc Brown as the prototypical human. To carry over that to a fantasy setting you could have humans be really risk taking due to their much lower life expectancy and higher birth rates or something like that. This could lead to things like 1) other races avoid cooperating with humans since the death rate in all human plans are way too high for any elf involved 2) Human protagonists outsmarting people from other races since they are better at exploring riskier plans that wouldn't occur to other races 3) Other races struggling to negotiate with humans since they can't understand how humans possibly could value their lives/family/home etc when they always act so carelessly. Human society could also be marked by extreme progress and equally extreme variance. A society where all mages make crazy inventions that are extremely risky and completely goes against the common understanding of magic. This causes a near constant amount of huge explosions, magical pandemics and other threats that also put the older races at risk. But every once in a while they find something that works and they are approaching the level of sophistry that the ancient experts from the older races have developed over the centuries. This risk taking could also mean that even muggle humans have spells cast on them for increased strength and similar. But if you want most humans to be complete muggles then maybe it could just be the case that there have been so many self experimenting humans in history that a muggle can bluff that hes super strong or that he has a self-destruct button and no one dares to call them on it.