This doesn't make any sense.
One could rack hundreds of hour of early games because he likes the initial phase of discovering the galaxy, then drop every playthrough as soon as he discovers it, because midgame is intolerably boring to him. Another guy could have racked up hours just for achievements because he is a completionist. Some others could have sunk many hours just to try and see if the game was worth the money spent on it, and then drop it. Another important factor is the sheer number of patches/DLC that allow a player to try new things quite ofted, maybe hoping the new features will ease midgame boredom, then discovering they don't and dropping the game again.
Having a lot of hours in a game doesn't mean it can't be a boring game.
I agree with the rest of your post, though.
Or you can be like me and minimize things when you aren't using them, then close your laptop and wander off. Then finally quit the application later on after Steam has logged 27 hours of playtime... of which you actually played 30 minutes. My point just being that logged playtime isn't necessarily how much time you spent playing the game. It just measures how long the application has been open. I officially have hundreds of hours in the game. I've actually played a fraction of that. A small fraction.
The problem that I have with the midgame is that sometimes I'm just waiting for the end game crisis to happen. I can't or don't want to go to war so I'm just building up my fleet to prepare for it.
Adding more exploration isn't going to fix that. The Great Khan mid game crisis can be fun but it only fires sometimes. Internal politics is the obvious solution to the "boring midgame" but Paradox simply haven't managed to get it right yet *shrugs*.
Tl;dr: Stellaris needs a strong theme to give the player goals and to drive conflict. The devs should stop adding new events, should stop focusing on "content" altogether, and should focus on tying the existing mechanics around one central idea.
I agree with this. Someone else mentioned earlier that they have been adding non-exploration mechanics in the last two major updates, and that's definitely true. It hasn't worked all that well though because game still doesn't have a sense of coherency.
Not to beat a dead horse, but I think this is a lot of why the game's mechanics don't connect together well (if at all). You need a central theme or idea to organize your game around. In CKII, for example, it was the politics of personalities. In HoI it's outright warfare and conquest. In EU I would argue that it's national destiny. Those games work because the theme gives the player goals and the mechanics can be built around advancing/hindering those goals.
Stellaris' idea is exploration. That doesn't work well because exploration is an inherently solitary and static project. Once you find something, it stays found. The map you uncover stays uncovered, the anomalies stay explored. Exploration is just a scavenger hunt. There's nothing dynamic about it, and once you meet the other players on the board it ends. Nothing drives conflict because you and the other player don't have interests that could compete.
The updates haven't really fixed things because they've been scattershot. They feel like a grab bag of cool "what if" ideas rather than coherent mechanics with a clear purpose. Stellaris needs a different, better theme to take over after the exploration ends. Then the devs can build mechanics that tie into that, helping the player achieve his/her goals and get in the way of other players achieving their own.
To put it another way, we have a whole bunch of new mechanics around fighting wars, but still no good reason to declare war. A whole bunch of new mechanics for running an economy, but nothing to build toward.
Without a theme, there are no goals. And without clear goals, you spend the game just waiting for something to happen. And it never really does...