Guess what I see? Tabs. Wasted space. Excessively large controls. Extra detail that PokeGen simply doesn't have added. However, I do have to agree that it has a certain appeal to it. At the same time, the way PokeGen is packed with information in such a small space is maybe more appealing. It's certainly more convenient to more people from what I've seen, including myself.
Sure, I could add even more images and detail on items, attacks, Pokemon, etc, but it just bloats the file size (not that that's particularly important, though) and increases the size of the dialog needlessly. Don't forget that people use it on laptops and small monitors. These have lower resolutions, resulting in less pixel space for the window to fit in.
Edit: Btw, even though I mostly disagree with you on this, having discussions like this does help to fuel my interest in continuing working on it, which is appreciated.