Warning - incoming rant.
I tried MoO3 when it came out and thought it was awful, a huge let down for a sequel of my favourite game. But I also played the game a few times since. Every couple of years I convince myself (mostly after playing MoO2) that it could be fun, it really could. I am always proven wrong. The game is still a mess even with everything the modders could have done for it. Here are the good sides of the game - first, it is really, really big. Lots of stars, lots of planets, lots of technologies, it's great for players that want long games. Also, I like the concept of starlanes because it allows you to clearly define core and border worlds. It even starts off interesting - stars to explore, planets to colonize, a large tech tree to work on.
Now for the bad sides. I get that they wanted to put a bigger focus on macro management, fine. But did they really have to make micro management so insanely annoying to do? Why the fuck are there only three slots on the two build ques every planet has? Why is there no simple auto build function like there was in MoO2 that wouldn't mess with economy sliders, build troops and ships I don't want and actively try to bankrupt every planet that has increased maintenance by building unnecessary buildings on it? Did they deliberately try to make it a pain in the ass to control what planets are doing? If so, good job. Once the number of colonies grows to over a hundred trying to make them do something makes me want to smash my head into the monitor.
The "tactical" combat, oh boy. It's just blobs of ships shooting at each other in real time without even the ability to pause. In an impressively bold move they managed to gut everything that made ship combat great in MoO2 and make it look much, much uglier at the same time. Individual ships are meaningless. Hell, armadas are meaningless. When fighting a mid or late wars you and the AI just send wave after wave of armadas at each others. Waves that the AI can apparently pull out of his ass and keep them refitted with new tech (where refitting ships is of course impossible for the player). Before this game I could never believe that commanding thousands of ships into battle could be so dull.
And those are just the big things. Many of the previous races have been killed off simply because the designers didn't like the way they look. Now they all look ugly as hell because the game artwork is just awful. Fuck, the whole game is much uglier than its predecessor. User interface in particular is ugly as hell, overly complicated and gives next to no information about what various options actually do. I have a sneaking suspicion that the answer for most of them is "not much". It's almost impossible to trade tech. Leaders die like flies. Your people automatically colonize every rock they like, no matter how useless it is to you, quickly inflating the number of colonies and there is no way to stop this. You can no longer choose the tech you want, leading to imbalanced research because getting what you desperately need is now simply a matter of luck. What the fuck is the point behind all those task forces anyway, does anyone actually use anything except armadas in wars? And how does that work anyway, do ships get fed-exed across the galaxy to where you create a task force?
Fuck, it's like someone went over every single part of MoO2 and looked for ways to make things more complicated while at the same time taking all the fun and charm out of it. Economy, research, ship design, war, diplomacy, spying, everything. And they killed the franchise doing it.