Honestly, was it focused at all on internal management even before the old pop overhaul? Because I don't remember it being that way in the slightest. It's more that every other aspect of the game got overhauled/updated/improved, and internal politics is last on that list. Next update after the Aquatic pack almost certainly, so soon(tm).
To a degree it was, back in the old times, Stellaris was a fair bit more bare bones, so the internal factions, sector management, ethics and the species your empire had were some of the more granular interesting features. But since then, it's the external systems that have received overhaul after overhaul, addition and addition. To the point where those internal features have fallen to the side greatly.
Please elaborate for the benefit of those that don't have I:R.
Pretty much this
In imperator you have your goverment, Like stellaris
Your goverment has factions, Like stellaris
This is where it immediately differs, the factions have an active role in your goverment, your pool of leaders, come from families, which all belong to a faction.
If your leader does well in something, his family gains prestige, thus his faction gains prestige
What I'd essentially propose for stellaris is
All Nations have 'factions' they already do really, based upon the existing ethics that pops have in your nation (So the Pacifists, and the Egalatarians to give an example)
These factions are from where all your leaders come from, every leader, governor, president, etc will have a faction, and there perks and agendas will be influenced by their faction
The better a leader does, the more this increases their factions prestige. The more pops will adopt their ethics.
Say you have a Militarist faction leader, he might have really awesome stats, but belong to a 'minor' (Say one/two pop) ethics faction, he goes off and destroys the enemy in a military war, because you chose him for his stats, and he did well, this could have the knock on effect of suddenly 10 militarist pops now, on his home planet or something, and maybe he's gained a shitload of prestige in general, so come next election, he's the first choice, he gets in, and has an agenda to build a bunch of defences, he kicks us, and so by the time he's out of office you end up with a 25 percent Militarist population. Idunno, I'm just spitballing at this point, but there's a dozen of other ways they could make the system interesting, doesn't have to be this.