What? I would put Ros as a very good example of steamlining. Rewatch season one. She's a source of exposition and introduction for Theon, she's used to elaborate on history through Pycell, she gives you some idea of what Littlefinger is up to—she was a great way to work information into the show.

Almost EVERYTHING they've cut was either nearly impossible to work into a TV show or was never supposed to be in the story to start with. Dorne and Quenten and so on were filler created to make up for the removal of the five year gap, same with Brienne and her useless jaunt through the Riverlands, a good chunk of the ironborn stuff and Moonboy for all we know. They did a pretty amazing job the first four seasons, with LSH being the only glaring omission that I've seen much complaining about. Then they reached AFFC and ADWD material and have to try and turn a massive pile of largely uninteresting filler into a coherent story. If they had just cut Dorne completely, along with a few other things, it might have worked—but they also have to pander to fanboys who care more about a single speech not being included then the fact that all the context to make that speech happen would require a solid hour of exposition, plus introducing several character's.

Especially since we don't actually know the way the story is supposed to end. I suspect that a huge amount of what was cut was removed because it's a red herring or otherwise unimportant to the end goal. Aegon is probably number one on this list. Lady Stoneheart likely also qualifies, along with the overly complicated mess that is Dorne, most of the politics in Meereen and so on.