i have to agree. i've never won a game by conquest yet, i just quit when my victory is inevitable. conquering and trying to defend all those cities is just boring, especially given the way that the AI spams units everywhere.
At least some way of turning over control of the city to an AI governor would help relieve issues. As would some kind of fortifications that can be built by non-fortresses, so i don't have to repeatedly rush new units before i can move on
if i ever do win a game by comquest, it'll be through stockpiling mana, and spamming curgen's volcano. it's just so much less effort than doing things manually.
as to razing, the 5 turn waiting time is annoying and doesn't make sense, i feel. I'd much rather see you able to START razing a city right away, and have the city be gradually destroyed, building by building, over a period of turns proportional to the level of the city and number of structures in it.