The replayability comes from randomization. When you play EU4 or Victoria, you pick a country and you immediately know who are your neighbors, who should be your allies and what should be your immediate conquests. Stellaris replayability comes from not knowing anything. Perhaps your neighbors hate you, perhaps they're willing to like you, perhaps. Also randomized technology means you can't plan on having specific technology paths.
You won't have historical 'scenarios', but each game will be different.
Randomization does not guarantee the player to do different.
Like sorting out a pile of random chips. In the end, it is always the same: sorting out.
Stellaris could not support a non randomized technological tree as it boils so much about doing the same thing.
In other PGs, starting as the same country only leads to do the same thing when the player aims for global domination.
In the other cases, the dynamic evolution of the board guarantees that the game experiences are different.
Starting out as Brittany in CK2 might mean conquering back the ancestral lands from the Germans to found the celtic empire.
It might mean keep Brittany small and guaranteeing its independance by installing your dynasty in neighbouring kingdoms.
It might mean conquering and forming France, use that powerhouse to carve a kingdom in the holy land, then do a plantagenet by granting independance to France and live on as the Kingdom of Jerusalem
Etc
The board dynamic evolution provides a wealth of scenarios on the fly that the typical PG players are not interested in since they are only interested in global domination.
I haven't read the review, but yeah, it seems like it's somewhat incomplete. It only has two victory conditions: 40% of all territory conquered or everyone killed.
This makes the end a very unsatisfying drag and not much of a choice.
Incomplete? Maybe not. Actually, PG players are mostly interested in the global domination game. They never got in the diversity of the other ways provided in PGs.
In this regard, S is the product that keeps to their tastes. They want global domination and S gives it to them.
S is reduced to the essential.