Training wheels are useful tool for beginner cyclists, but not useful for advanced cyclists. Likewise, quantum ogres are a useful tool for beginner DMs, but not for seasoned DMs.
Quantum ogres are a white lie to your players with a result that, at best, doesn’t actually do anything. At worst, the players figure it out and call you out on it.
The reason they can be helpful for a beginner DM is because they help people who want their players think their choices matter, but are afraid to actually give them that choice: “I want my players to do X but I don’t want them to think they were forced to do X, so I’m going to give them a false choice and then do X anyway.”
Let’s say the players are walking and see a sign for Town A and Town B. Whichever they choose, the DM is just going to sub in the same town they prepped. So why put the fork in the road? We pause the game, have the players deliberate, and ask them to make a choice: we’re investing time and effort into a decision, but why? To make our players feel like they matter? In reality, the scenario is much cleaner if we just have a single road to Town A with no fork.
Adding just a little bit of information actually makes the decision matter: “Town A, population 3000. Town B, population 36.” Now they have some information to make a meaningful decision. Add some foreknowledge that Town A is a major port city and Town B is a small farming hamlet, and suddenly the choice becomes interesting. Now we can see why the quantum ogre is actually a hindrance for a seasoned DM, much like training wheels are a hindrance for an expert cyclist: by giving players more information, players can make a meaningful choice that has an impact on the world.
This remains true even without the context. For example, having multiple paths in a dungeon let the players experience the content at their own pace and in the order they choose, even though they typically don’t know what content to expect. Letting the players choose which order to visit Rooms A, B, and C makes the scenario richer than just quantum rigging it so the players must always experience A, B, and C in that order no matter which room they pick. Pushing yourself to do this when the choices are more arbitrary will help you get off the training wheels faster and help you develop richer, modular content when creating a true open world, like above where our players can freely choose between two very different towns.
In short, using a quantum ogre once or twice while learning won’t make you a terrible DM. But petting your players freely choose whether to go through troll territory or ogre territory and tailoring your encounters accordingly will make you a much better DM than simply teleporting the ogre.