Welcome back In short could be better, could be worse. Though you can say that about most things more or less CA2019 is particularly nice with some decent point changes and the PA stuff is delivering some character as well as buffs - but this is not a full solution. This can only really come with the next round of codex updates whenever that may be.
With Cultists and CSM down in points you can farm CP more easily if that's what you need, generally speaking you can sum it up as more or less the same as before albeit cheaper with PA Warlord and Relic additions to taste. There's a topic on fighting new Marines here that will be a good read if you're thinking about how you face them. This one covers CA2019's point changes. Both will be good to catch up
So you may have a tough fight against the new Marines as they benefit from being recently out the door and GW showering new toys on them, but otherwise you'll have pretty decent games against others It's the old codex creep essentially, though we've yet to see how it plays out as it has only just started so it's possible that future updates will be levelling playing fields rather than remaking them. We'll all need to wait to be convinced of that I have no doubt!
The game truly rests on your opponents, as always. If someone wants to play a Beard-9000 list that flicks you off the board so nobody has any fun that's not a new development in 8th... You can have decent games against C:SM, though even without the latest and greatest they'll still be strong overall as it's a good set of rules. That said, you can substitute "C:SM" with other codices in previous editions too. Nothing new under the sun as the saying goes
Ultimately it's your hobby. If you want to get your Chaos out again that sounds like all the justification you need to me Feels like we're a way off the next codex release, whoever that will be for, so plenty of time to get your CSM battle ready then?