Few are gifted, all can learn. Havelock1000 points out that since there is no necessity there will be no development which means no firearms because there is no need for it.
That is like arguing that well, we have swords and they kill pretty well, so why bother inventing bows and arrows?
Even without "necessity", inventions happen. And to claim there is no "necessity" in combat - a situation where your own like is at stake - is preposterous. Nobody wants to die. Everyone will try and find a way to not get killed. Eliminating threat from far away is one of the best ways of doing that. And guns are best are killing at a distance. That's why we're not using bows and crossbows anymore.
Even if magic was available to everyone and very easy to learn, people would still invent guns - because, in the possible scenario you run out of Magicka, it's better to be a mage with a gun.
At the end of the day I don't care how many reasons there are for technological advancement in TES, I want one of the last medievel fantasy series to stay in that technological stage.
I also don't want guns in TES. But saying there are no guns because "magic" is just silly and makes little sense.
How about simply assuming there's no way to make gunpowder? Let's say there's no sulfur, potassium or nitrate on Nirn. There, problem solved.