Johnson comparing backstories of Snoke and Palpatine disregards one key element:
In the OT, Palpatine was the head of the galaxy's established government, the one that was already in power when we picked up the story. Us as consumers accepted this fact and proceeded forward, because there inherently wasn't much explaining to do. He was in charge, the end.
The gaalxy's political makeup is more complicated as we begin TFA. We have the New Republic, and we have the First Order. We also come into the ST story with the understanding that the leaders of the Empire perished in ROJ and the Empire was left in tatters. So the natural question to ask is, who is the First Order, who's in charge, and how does that group exist within the New Republic?
This is part of my problem with the entire premise of the ST to begin with. ROJ had such a fairy tale happy ending, how do you continue that story in a necessary and compelling way? ROJ almost did too good of a job of tying up all the loose ends to keep that particular story going. If a "new Empire" arose (First Order) and someone was in charge of that group, how that person came to power is a necessary story to tell in order for a ST to have relevance, given what's come before it. Who Snoke is matters in the big picture, and Johnson/LFL decided it just didn't matter. I'm sorry, but this is a disservice to the integrity of the story (forget the fans for a moment). The story loses its punch when you remove any references to how the important characters came to be. We knew Palpatine was powerful because of Vader's deference to him in ESB, so when he directly enters the story in ROJ, we know what a big threat he is to Luke and the rebels. The story construction is logical in that case.
When you combine TFA and TLJ, Snoke is rendered more or less pointless, because it is Kylo Ren who Hux refers to as "Supreme Leader" in TLJ's final scenes on Crait. So the First Order had, and still has a supreme leader, but it's a different person in one film than the next. If we know how Snoke became the supreme leader, it would make the transition of that title to Ren more important. The way Snoke, in the big picture, has been handled, it screams lazy and/or sloppy storytelling, which is something you're bound to get when you have more than one filmmaker attempting to weave these stories together. There are examples of this in TFA too.
Look, I love and accept Star Wars for what it is. I especially love the prequels, but that doesn't mean I don't acknowledge its flaws, or ways it could be better (make the Trade Federation a more deadly threat, put Dooku in TPM, Grievous in AOTC). Many prequel haters say they don't like it because it didn't match their specific vision for Ep. 1-3. Now, I love Luke's characterization in TLJ. Spot-on perfect. But I would have changed other elements of TLJ, had I been in control. But I don't dwell on that either. I accept it as part of the larger story and move on.