No, it's actually possible. In fact, it's happened. I am currently playing a Way of Mercy monk, which is FAR better than any monk sub-class in 2014. Yet all of the old books still work fine. We're still playing 5e. All that changed is monks got better.
So if you are still playing through, say, Lost Mines of Phandelver but now your Ranger is better, I don't think most of us would see that as fundamentally a new experience. But you try and run 2014 PHB rules with a 4e adventure and see how that goes.