Regarding Dominions micromanagement, it's not as bad as Dom3 was, so at least part of it is just lingering reputation that's less deserved these days. Additionally it varies. Blood magic has a bit more micro, as do Communions if you use them. Neither of which are mandatory or even possible for a lot of nations. And even then you can do very complicated communions or very simple ones, same as you can be very efficient and microintensive about your Blood magic or you can do it in more broad strokes, losing some efficiency but retaining more of your sanity
Sure there's some micro everywhere, but we're talking about a (very war focused) 4X, there's bound to be some micro as the game develops.
Just don't join more than one game at a time if you're worried, as the micro increases steadily and you don't want to find yourself in the middle of three endgames at once.
Also I never did the tutorial (only got on board with dom4 about a year ago), and while I've certainly browsed through the manual, lot of it is stuff that you pick up elsewhere if you're the kind of person who likes reading community guides and whatnot.
Dom3 MP scene is mostly dead, there's little reason to get Dom3 these days as the price difference isn't huge and even the SP parts of it are moderately improved.