Tips for running Craft in Microsoft IIS
I run Craft on IIS/Win 10 on my main development box and don't have issues with it.  Don't recall having to jump through hoops to get it working, either.

I suspect it's more of the "shared server" that's the issue, but you can start by enabling devMode in Craft and check the timestamped profiling output (code and database) in the browser's console and craft/storage/runtime/logs to try and narrow down where the time is going.