I've been in the seat many times and have been a player a lot more times. Anyone can be a DM, but being a good DM is an art.
I've had some good DMs, I've had some bad DMs and I've had some mostly average DMs. The worst DM I've ever had, had us slaughtered by 70 level 15 paladins when we were level 3. We weren't even the main target of the 70 level 15 paladins; who were incidentally razing a good-aligned town in Eberron. This was back in 3.5, where paladins insta-fell if they did evil shit like this. And that was when I brought a friend new to the whole D&D scene with me to play D&D and this happens. Needless to say, it didn't turn out well.
I think the most common misconception people have of a DMs role is that of an adversarial role. The DM isn't there to oppose the players, instead the DM is there to facilitate the players as well as the storyline. Any DM that thinks his role is to act as an antagonist is probably doing it wrong and not running a very enjoyable game.
The second most common misconception would probably that of the DM as a pure storyteller. We've all been there, you have a story layout that you want to follow as a DM and you want to follow it but those damn pesky players keep derailing you by asking for random stuff and then doing random things like creating Hydra in Faerun. Eventually, you end up being so fed-up you railroad them all the way. Can they make a charisma check for this? No. You fail. Can they try to escape that way? Rocks suddenly fall and that route is caved in. You know the gist, things must occur according to PLOT and no derailment whatsoever. The problem with this approach is that while it's better than the first, it also makes for a very boring game for the players who feel like they have no agency and are basically just railroaded along the game. This has all the interactivity of a QTE event for videogames. As someone put it, if you just want to tell a story, go write a book.
In my opinion, being a DM is a bit of push and pull (hence the yin yang symbol). Much like players can't play without a DM, DMs can't DM without players. It's no fun to just stick to the storyline and restrict player creativity; even if it really gets pretty fucked up at times. Instead the best DMs take whatever players can throw at them and adapt to it. Want to create Hydra? Then suddenly, a mysterious Paladin with a magical shield shows up to try and thwart you. The important thing is to let players feel like they have some agency in the world and the ability to affect it the way they choose to. Sometimes they may just want to kill their way through the Cave of Orc-evil or other times they just want to talk/sneak their way through to the final boss. A good DM allows for both possibilities.
Also, a good DM allows for players to buy magical items whenever they want. But that's just me talking.