I played around with the theme editor a bit last week and my observation is that I think it was partially released to show how complicated and difficult it is to produce a theme! :)
This is not a knock on Cakewalk - this is just how it is. Changing a few colors is one thing, but actually developing a theme is something else. I do web design as a part of my business and we talk to people every week who believe it is "simple" to build a custom website, then they show us what they've done and tell us how much time they spent to get there: it looks bad and took 10s of hours to do and in the end, they determine that building a full site on their own is not for them.
I am very familiar with my image editing software and I thought it was really cool that I could basically directly edit the graphics from the editor, save them back, and have them "live" in the editor.
I thought that the most difficult part of this is the sheer number of items there are to edit and the fact that there are no "macro" level changes to make, like "make all of the button background look like this" and choose a color or make a gradient. It's a lot more piece by piece than that, and that can get tedious really fast.
The same design principals apply here as with anything: know what you want to do before you just dig in and start changing things. Pick your color palette, know where the elements are that you need to change, and be complete. It's a LOT of effort.
I think that this should bring a new level of respect to the creators of any themes, whether made by Cakewalk or by the community.
Happy to see the option for those who want to really dig into the customization.