Thank you for playing the game!
a good game should explain its mechanics without a tutorial so I agree with capturing buildings is not works very well. I planned (but not implemented) enemies could also capture buildings, which would make you want to garrison buildings to protect them.
Also, the problem with mouse is caused by script written by myself combined with WebGL build. I tried to implement double click, drag select box and simple click. However, it is not working as intented.
I will try your game as soon as possible, again thank you for playing the game and leaving a reply :)