I strongly disagree with you there, i think spirecraft are much more powerful at any time then golems and even fallen spire fleets. It's more of a meta thing though as they arent actually strong, what they do is enable strategies that wouldn't exist otherwise that are very powerful (and annoying to use).
Attritioners+gravity turrets will kill all medium and high cap fleet ships on defensive chokepoints, martyrs+cloakers take giant chunks out of exo waves, implosions under forcefields melt the high HP threats (but i never use them because their model is so large it's really unfun to try to fit them all under forcefields), jumpships+pausing means i can dump a couple high mark starships right on top of any target 15+ hops from my territory and erase it (works even against enemy homeworlds).
And remember that no territory needs to be taken to get spirecraft, just bring a protecting fleet, a builder and engineers in bad guy space and take their rocks.
I do enjoy golems much more though because getting the most out of spirecraft is pretty micro intensive while golems just go in the blob and kick butts. That's the real reason i usually don't play with spirecraft, way too much work, but i have played with them in my recent games. I do hate that golems still need to be turned off to avoid eating resources when not fighting. I hate all the boring micro.
The problem i'd like addressed with #1 above is that the size of the first exo wave is too big for the toys i've had time to bring online to deal with it, by the second exo it's a challenge but i have enough options for a good fight.
edit: for reference, in my last game i had to reload 3 times for the first exo until i got a beatable one.
As for the AI homeworlds, I don't find them too hard, I find them not enough fun and too long, so i usually start them, get bored, quit game.
For #2, no one else finds plasma eyes *much* stronger and harder to deal with then all the other eye types? I'm very thankful for hackers with that option having very low cost, i would probably have simply quit my last game when there was an AI chokepoint with 3 worlds in a row with plasma eyes if i couldnt have hacked them away.