
Okay... I'm going to demand/request all the people complaining eternity is too short a game by speed and the average tech takes 6 turns explain what their person skill level is set on, asuming custom games. I'm playing on nobel (though I've managed to beat a game so I'm thinking a skill level upgraded is soon needed) for everyone and as a

booster Leader I can't average out at that speed. Sure If I bulldoze through things and skip all the military only techs until way later I could pull that off. They get to that level of researched later and I can mostly do that... but that means my defenses are level 1 swarm tactics. Which kills actual building of buildings speed. For me its closer to 8-10 a tech, with a

Leader. Some techs being more like 15-20... some in the 30s or 40s. Construction being the most blatent for me.
In short, you may need to add modifiers for the average starting power teir of the Civs... human and AI. AIs getting a bigger bonus to

at that level then the human players or like adjustments.
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Back to the building issue... basically the same thing I said before only with buildings instead of techs. If you built some or all of the buildings being obsoleted it (the lastest on that building tree(s) only) should speed up the replacement buildings. Several buildings on different paths rolled into the new one even greater bonuses. Perhaps some future, relative to the tech granting that building's construction speed, techs should add

speed to old buiildings. Things like that.
So a list of the ideas to increase building speed:
1) Make certain buildings change their bonuses via civics. Some buildings are apparently taking up realistate until a civic is put back into use. Vaguely disturbing it is the number of derilict/reminder of past age buildings involved in this. For example, the Conscription building and Recruitment Center are the same physical building repurposed. Its a matter of red tape to switch between them and that should be part of the lag anarchy causes between civics. Look at all civic reliant buildings and make them more generic, with civics specific bonuses.
2) Reward the Civ for having built the now outdated tech by adding a

bonus to making the next rev up. Your upgrading and can use the old building until its replacement is done. Particularly with the huts. Your actually using the old housing and demolishing them only after a new place in built. You can use the old production buildings to help construct their replacements.
3) Make it so huts, subburbs, palaces, highrise and such will automatically upgrade themselves... though a temporary

and/or

negative may kick in to cover the cost. Much like with terrain improvements like mines.
4) Make roads get a building bonus for the highest level road already built on the square. cartpath/mud path/road should grant an easier build time with mudpath/road/paved road as more and more of the ground work is there. Same with the railroad upgrades.