Going back to an old title to add content is by itself not a bad thing. It becomes so when what you do, does more harm than good. My reasons why this update is something that does way more bad things than good things.
1) First off, and this is incredibly important. It breaks mods. A lot of players had a finetuned collection of mods to get the game they want. With this update, a lot of mods will be obsolete. Bigger mods will probably be updated, but the fate of other mods is uncertain. There was an equilibrium, and that has been disrupted for no good reason.
2) secondly, this update doesnt fix any of the problems vanilla rome 2 had (agent spam, bad diplomacy, bad CAI). It just adds a shallow gameplay layer to it (why shallow is explained below). If anything, it reminds people of, even though rome 2 has come a long way, there are still a lot of flaws and frustrations about it.
3) now onto the gameplay itself and why it is just one big failed opportunity.
a) Its good statesman have a use, the problem is their abilities are so irrelevant
-Administrators make it even easier to just conquer and leave regions as they are pacified more easily/ to steamroll the AI. you never need to garrison settlement anymore.
-Diplomats get themself killed or make things worse in 80% of the cases. I have a -75 diplomacy modifier with one faction, thanks to incompetent diplomats, even though they had good gravitas. And even when they succeed, +5 or 10 relations barely does anything
-you should never have a lack of food, organising feasts is just a waste of money
And does the AI use its statesmen? offcours not. In over 150 turns I didnt receive one diplomat from an AI faction. Imagine how much more immersive it would be if the AI uses this new feature to have some interaction with you and you can actually respond to it in the way they do.
b) Having secession is a more realistic and interesting way of handling big empires than a random civil war. The problem is that the loyalty system feels so artificial and unresponsive that it doesnt improve the game, on the contrary. Loyalty gets a penalty for each imperium level, and in itself doesnt have any positive benefits. The only benefit you get is not having a secession. Even though loyalty might be high, opposing parties will still do their annoying things of trying to bribe/adopt or even kill your family members. And now you can't even retailate against it, because it will drop loyalty. The AI tries to assassinate my king (twice), and I can do nothing against it (purging or other things just increases the risk of secession). I do get to deal with their petty pieves of not liking foreigners, or wanting more farms,... Imagine that really working this system gave real benefits. Like increased research speed, or more tax from regions that are in control of a loyal clan. Or a morale boosts to troops of loyal clans. Now its mainly dealing with annoyances. Its a system that punishes you for not dealing with it, but offers no rewards for using it. that's bad design
c) Also, political events are incredibly poorly designed. In fact, the only new political event I had was "riot in the capital". 8 times, for no good reason. That doesnt help my immersion. It gives me the feeling you were lazy and didnt bother to make any more (other culture groups might have more, but why give politics to all factions if you only focus on a few). There are so many possible things that you could have made events around, and you didnt do it. thats just sad, and again, makes it feel artificial.
d) the government system is another wasted opportunity. When out of a choice of options, one option is superior to the others (empire in this case), its not a choice anymore. You will visit this screen twice in a whole campaign. First time to see what you need to form an empire, the second time to actually press the button. That has little added value. Imagine that different goverment types actually required you to make a choice, or different government types help with each of the different victory conditions. For example, the confederation gives a bonus to recruitment and military costs, while the empire receives an economic and cultural boost to help with those victory conditions. Its again a shallow addition
Summary: power and politics is a wasted opportunity to improve rome 2 and does more harm than good. The only improvement is the UI for skill trees. Except we already had the excellent TTT mod for it. It very painfull to watch how CA squandered another opportunity to do something for its historical fans, instead of giving the impression the historical games are being worked on by trainees and B-teams.