The start of the game is a bit slow for your city development because there is hardly anything to build. The first few things are obvious with merchant, study, temple, garden/farm, command post, workshop, and hut. After that though there is not much and you have lots of space remaining with nothing to build. I know that sounds like a lot but it's not really and often times you end up with nothing left to build and extra spaces. So you end up waiting for a long time till the city levels up and you can build more of the "standard improvements".

The problem with the standard improvement limit is at the start of the game it's a huge hinderance from getting your economy rolling. While late game it become almost meaningless. With the ability to build 3+ of buildings that are 2x2 their size is more an issue the the standard improvement limit. With the larger higher tech versions of production buildings being unlocked both with city level and R&D the result is late game when you could build 4 merchants on a single game tile it's much easier and more effecient to build 1 market plus you could still build 3 more market's in that level 4 city.

The other down side of the limit is it discourages specialization by making it nearly impossible. Only larger cities can build a lot of one building type. This combined with lots of later tech buildings won't be unlocked until you have been playing a while means that most cities will be very generalized at the start and for quite a while into the game.

I propose simply letting the player build as many as they want just like with housing and gardens. Of course some buildings remain as unique so that only 1 is in the city. But the ones  you can already build multiples of I say drop the limit so we can specialize our cities.