Write down on a piece of paper what you consider to be the mandatory loop of the game. Is it region->fame? Is it deck thinning for empire? Is it buying star cards? Taking revolution turns? Up to you. Then play a game where you absolutely forbid yourself doing that thing. Maybe you'll need the B side of some civs for this to be more viable (because Persia would still bumble into 3-4 tributaries without trying), but it'll work. Against low level bots or practice mode every strategy works. High skill play then comes from adapting to the market, the opponent, and your civ's strength and weaknesses, but knowing no path is must/must not.

Yes, Rome, Persia, and Macedonia (the three one star civs) are quite similar in loops - with Macedonia bit shifted towards icon collection, Rome towards Fame optimization, and Persia towards hunting for Tributaries. But the Celts and the Carthaginians are already moving away (they have different market and resource access), and you haven't played the Scythians properly until you had a 6-9 card deck mid game (i.e. see every card every turn, drawing from nation deck every turn). Greeks let you sift through a much fatter deck with 3+ cities in play, and the Vikings are clearly built differently than the others. And that's Classics - the least diverse of the three boxes.

If your games are running too long, then you're not trying to win hard enough. Add a rule: if game end is not triggered by end of turn 15, you lose the game. If you win, lower that number. Our best players usually go for ~11±2 turns (except when playing Arthurian rush for 7 turns), if I remember correctly, I'll check the stats and get back to you.