I think this is a bit of a passion project for Johan, and it seems like he also wants a revanche after the somewhat disappointing EU: Rome (at least I got the impression PDX themselves were somewhat unhappy with how that game turned out). That gives me quite a lot of hope that the foundations of the game will be solid.
It does build solidly on the core game design pillars of Paradox games, especially the use of various kinds of "nation mana" as the core resource enabling and limiting actions and development. The warfare, battles and military aspects are based on the usual model as well. The mix of character and nation-based gameplay is somewhat new, as is the pops model (even if it does show roots in Victoria and Stellaris), but nevertheless, I think if you like Paradox games in general, you will like this game, but if you don't like the way Paradox games play, you probably won't like this either.
A lot of the Paradox mechanics rely heavily on iteration to hit a sweet spot between micro-management and the good kind of busywork. Stellaris gave up on the tile model (wisely I think, as it was such a departure from their usual mechanics, that they'd need too much iteration to make it work) and there's historically been some issues making pop-based models work - there seems to be somewhat of a love-hate relationship with how they ended up on Vic1/Vic2/Stellaris. The character mechanics of CK2 have been a smash hit, so I'm very excited to see an attempt at integrating these into a non-CK game. Stellaris is sorely missing better character mechanics, and I think if Paradox manage to get a good balance between a pop-based economy and a character-based narrative in this game, it's very likely we'll see those systems ported to Stellaris.
Either way with how Stellaris is evolving and what we're seeing from Imperator gameplay - Paradox really seems to be converging the overall mechanics across their games. As someone who enjoys Paradox games, I think that's a great thing. The oft-heard accusations of their recent games having too much EU4 DNA is unreasonably harsh, but not entirely incorrect either, so I am glad to see further experiments with characters and pops. Stellaris did regress a bit much towards EU4 after the great purge of tiles.
My biggest worry is actually that they decided to include India, Scandinavia and all of the British Isles - that could result in performance issues and some odd campaign results. I'd much rather have seen those resource spent on polishing and refining the world closer to the mediterranean. But hey, perhaps I'll be positively surprised. I still think the inclusion of India and Western China in CK2 would have worked better as separate "grand campaigns" - or even games.