Hello Samuel (or Sam if you prefer), thank you for your feedback, it's very much appreciated!
The people move by a set amount each frame, so on devices with lower frame rates, it may be that they will move slower for you. I'll see what I can do to remedy this issue, thanks for bringing it to my attention.
The game has been designed to speed up as it goes on. You can click anywhere on the screen to catch the robbers, I forgot to mention that. You can also click any time the robbers are actually on screen to catch them.
Finally, while having to choose which people to click would be a good idea, it would technically violate the "one-button" rule. It's a nice idea, though!