I think a lot of the changes made in Beta 3 have really hammered down a fun opening act for FE.  Sov/Race specialization, more aggressive monsters, battle tactical battle mechanics, streamlined spells, better AI.  The first 40 minutes to an hour of the game really shines.  However, after you've cleared out all the low-level monsters, and grown a few cities to level 3, the game starts to bog down again and lose focus.

I'm sure we'll see some big changes in beta 4 to address this.  I'd suggest that one reason for the midgame blues is that the current UI for building, training units, and casting spells is too clunky to handle more than a handful of options.

I find especially with buildings that I often don't know the exact building I want. I just know the type of building. Like I see that my city has stopped growing so I click into the Buil menu and look for a +food building. Now maybe the city already has maxed out its food supply or maybe there's one building remaining but I have to scan through a whole list of "not what I need" to find that out.  Or maybe there's three different buildings that provide +food, but they're scattered through the list which makes it trickier to compare them.

It's clear in this case that the number of buildings aren't the problem, it's the interface that is constraining the game.

I see these unsorted and jumbled lists and I think they cry out for grouping and filtering tools.

The idea would be you click on "build" and then pick the type of building like +food and you're presented with a list of available buildings that provide food. This would reduce screen clutter, make it easier to find the right building.

As an added bonus, as I implied before, this would loosen the UI's constraint on the number of buildings and the complexity of said buildings.  So instead of one +food we could have several with different trade offs because they'd be easily discoverable and comparable.