God, do I hate having to generate a city.
Hamlets? Fine. No problem. I even use this little system that makes it fun to do. Plus this thing, which is very cool as well.
But a WHOLE CITY? Gah! The sheer number of NPCs and professions and logistics to generate. No amount of random tables could generate all that. And when you finally get there...
...the PCs want to explore something else that catches their eye. Something you didn't have generated.
I think the reason I most hate cities is that they are the biggest preparation black-holes in the entire hobby. I've learned through years of heartbreak that prepping every detail of an adventure is just asking to be disappointed in your players, as a GM. So, I just record the big notes ahead of time, and make my way through the rest like some kind of jazz pianist.
But that doesn't work well for cities. There is always another thing that needs to be prepped. If the PCs get in trouble with the law, then you need to improvise the city's police and justice procedures, potentially even the governing body. If the PCs want to go shopping, you have to figure out what goods at what prices and what availabilities are in the city.
If you don't, everyone will default to the standard city guardsmen, PHB goods and prices, etc. etc., and your game turns into giant scoops of vanilla ice cream scattered through a fantasy world that is, hopefully, more flavorful that its cities.
So what can someone like me do, to waste no time, but still allow the PCs to enter/use cities.
My thought is a carousing table. The city is just a place to rest, and you can either stay at home/in bed and be safe, or risk a night on the town and potentially get some XP, or your teeth knocked out of your head.
Here are some tables: number one, number two, number three.
This doesn't preclude the adventurers from actually exploring a city, if you have it prepared, or a PART of the city, if you have that prepared. But, it speeds up the whole process of browsing and twiddling thumbs and playing out each night of wild passion and drunken stumbling.
I like to picture it as a kind of fast-forward or montage moment in between the real important parts, aka the adventuring.