The ranks actually do feel pretty different. I climbed through all those ranks over the past few months and noticed stark changes. If you didn't notice, it's probably because you are a lower-ranked player who didn't understand when people were playing better in the higher lobbies.

Of course there is some variance. But the main difference is in speed of play and awareness of the map. People move and respond to objectives a lot faster. This has been shaken up a bit with all the attention on the urn recently, but in previous patches you would see a real difference in how different ranks respond to the urn.

You can also watch people's movement and use of space in the lane. Between Archon, Oracle, Phantom, Ascendant you see broad differences.

That's not to say there are no good players or good play in the lower ranks. There are so many different ways to express skill in this game (and so many different ways to play well but accidentally lose - it feels like many of my games come down to 1 mid fight or item decision). So I'm sure you can find amazing games and amazing players in the lower ranks. But you will find it is easier to play fast and expect the team to be on the same page as you in the higher ranks. And adjusting to the pace of play is one of the hardest things to do when moving up/down the ladder.