Will answer each item but parsing out a coupla comments here for emphasis. What you indicate here is more in line with "roleplay" type play. Otherwise, it is total bupkis..it's nonsense. You learn optimal gameplay and mechanics and play the map.
Wonders have a purpose. They either give you a powerful early benefit or you put bonus hammers into them for fail gold. Great Wall with stone is great for fail gold..it is good for nothing else. 2 Wonders obviously work well here - Mids and GLH. And since it is Noble, Oracle something is pretty easy without even trying.
I never build walls except in an emergency they are an easy 2pop whip, but not sure what GW has to do with that anyway.
Lagash itself is not bad...good Bureau cap option (although may be other places too). Problem is you orphaned a strong food resource. A city should have been on coast there for the fish. As mentioned Nibru spot could be 3 cities easily.
This is problem one of the harder things less experience players need to learn. How to balance economy with expansion. With that said maintenance is less severe on Noble. Just wait until you play higher levels. Cottages and trade routes help you fund expansion. Not sure if you discussed this previously or you implemented it but you should use the 100/0 % research guideline. Once you have Currency you are golden. GLH here means settle everything asap.
Lastly, your economy is probably not as bad as you think it is
see above. Astro bulbing is goto ploy in iso situations.
I'm not sure when and why you switch civics or out of slavery. I noted that it appeared you ran a Golden Age at some point, so maybe you did then and forgot to switch out. Slavery is powerful for a high percentage of most games. Space may be an exception since you enter late stages with various increases to natural production....and you grow cities large.
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ha..i thought it odd that bfc was better improved than many of your other cities yet no city was there.
overbuilding is a very common problem among newer players. Granted, again, in a Space game you may eventually build a few things to grow larger but your natural production skyrockets as well with workshops and State Property, and Factories.
Forests help you expand early and maybe get those coveted wonders. Worrying about health is helping win the game.
Not sure where you got that idea. Specialists match what you need to win. GSs usually the focus early for bulbing, like Lib path or ..in this case...even Astro path. Later GMs increase in value as GS bulbing loses value and running trade missions more important. Running a GE here and there ain't bad, but all the others are crap unless you have a specific purposes. But don't pollute the gene pool in cities until you acquire what you need.
I would never run artists at all except in a culture game. Great Spies are crap. Although any odd great person you might produce can be used for golden ages...but usually those pop randomly from some wonder you built or captured.
I vaguely do recall this. I do not do a very good job

Overall, your game needs a lot of work. You really need to take it back to the basics and learn how to successfully manage and conduct the early stages of the game. Basically once you get comfortable with strong early gameplay you can do anything with a game. And just for perspective, on Noble level, with just getting a few concepts under your belt, you should absolutely blow the AI away in every respect. I mean..let me put it this way...in this game - with maybe the exception of Archery, Theology (why did you tech that?) and Divine Right which are all techs I never tech - you should be light years ahead of the AI tech.
It seems you have some preconceived ideas about this game or learn some things somewhere that were not all that helpful. My point is you will totally rethink how you play.