try.drone.io is quite old and the screenshot on that page was a mockup only. Below is a screenshot of the latest user interface. I personally think it is quite clean, although good and clean are very subjective. The current user interface has received overall positive feedback (yes, there are rough edges, but they will be resolved) so there are no plans for major UI changes at this time.
Or if there was any possible ways to change the web ui or customize it?
You can fork the project and change the UI as you see fit. The UI is a single page web application so you simply provide an alternate index.html and serve your assets in /static. You will need to read through the code and figure this out on your own (I cannot offer my time, as I’m quite busy) but it is certainly possible and other teams (such as HP) are already doing this.