Your language looks like CSS, but it isn't. It's your own Domain Specific Language.
Ask yourself this: Do you really want to create your own file format, for which you need to write a parser. This parser needs to be fast and robust. You also need to document your file format and teach people how it works - after all, it's a customized language. You then need to be aware that you may run into issues you never thought of - maybe someone thought it's a great idea to create a 50 MB file and your parser crashes, corrupting a savegame or so. Or you decide you need to add a feature that can only be implemented with a breaking syntax change, thus breaking all the existing files.
The reason why formats like XML are so popular is because XML has these problems solved. You can find many great XML parsers that are proven to be robust, fast and leak-free. Also, many people know XML files and how to edit them, and because it's such a generic but well defined syntax you can be sure that you can extend later.
Your motivation seems to be easy editing by hand, which is common in community SDKs. Now, the reason people edit those files by hand is that they don't have the tools the Game Devs use. You can assume that a company developing a game for several years has some graphical tools for editing such files - they may not be great and bugfree, but they edit the files for you and developers only rarely edit them by hand in order to tweak something. Those tools are rarely released in 'Modding SDKs', so most modders edit by hand.
So my initial reaction would be: Instead of spending time developing a new, unproven format that is easy to edit by hand, I'd rather use a battle-proven format and spend the time writing tools that make editing easy.
But blanket statements don't work like that. It always depends. If you spend 3 or more years writing a big game with a sizable dev team, then you can spend a lot of time developing, testing and finetuning your system. If you have 15000 files to parse, then finding ways to reduce memory usage becomes important.
But for small/medium/indie games, I'd go with a known and well-supported format like XML and a nice tool to edit it.