For better or worse: Yes, it is.
Without being too scientific, what happens is that the flavours are bound to oils in the coffee bean. As soon as the beans are ground and exposed to oxygen and air, they begin to lose flavour nuances, and over time, the oils begin to taste rancid.
You can therefore clearly taste the difference when you compare freshly ground beans to a bag of ready-ground coffee bought from the supermarket. For a trained coffee drinker, it can actually be only a matter of minutes after grinding before the coffee begins to lose its flavour nuances.
It may sound a little overwhelming when we put it like that, but once you start drinking freshly ground coffee, it quickly becomes difficult to go back.