Overall what I lack the most is a *consistant* ability to focus and synergize all the "micro skills" I've learned into a fully coherent whole that properly leverages map, leader, and game option conditions.
What that means is, I can micro tiles, great. I can build enough workers and keep the army big enough to avoid unwanted DoWs. Great. I can expand enough, great. I know when early war is appropriate and when to expand into sweet empty land. Great. I've even learned how to (partially at least) let go of my tree addiction and CHOP more, great. And so on with just about all the narrow classes of skills we players pick up along the way.
But it's in the realm of putting it all together in an effective, coherent way, that I often get lost and frustrated. Not all the time. Sometimes I'm "on" and owning just seems to come naturally as things click and I naturally/instinctively fit all the micro skills into a mad long-term plan, and so on. But there are other times that the strategic pieces I try to fit together are like square pegs into round holes, and the non-fit and non-synergy doesn't become apparent to me until mid-game when I'm 2nd or 3rd from the bottom of the powergraph wondering how I sunk that low.
It's hard to think of examples off hand, but it's something like: I'll REX and focus on that, and nail down a sweet resource pool, near-orgasmic chokepoints, boxing in nearby AIs, grabbing their resources to nerf them mercilessly, and meanwhile fund the economy up so the expansion can keep at it, and prepare the way to rebuild when the critical land is claimed. Then comes the dreaded "toot toot toot toot toot toot toooooooooooooooot." DoW. What....? OOPS, I forgot to PROTECT that expansion, and now there's a Shaka stack of axes and impis marching toward my warrior-garrisoned cities. SON of a B...OUDICA!
Then it's back to 4000 BC, and I remind myself, "don't forget the military, dammit!" And then that time around I get clobbered by new random events, like a barbarian horde nuke or some other silly series of events, and the opportunity to fix my previous mistakes is lost.
Then I switch to Medieval Total War for a while, in anger, lol.
It's totally my fault, but I just too frequently lost sight of keeping all of the 20 to 30 dimensions of strategy together and holistic and synergetic.
And at the higher levels I just get bored as my every action is a read-off of some walk-through article. No thinking involved (and when I do break away and try to figure it out on my own, obviously I get slammed).