1. For my purposes, the weight isn't an issue and I don't see any obvious waste to cut. I think you've achieved your stated goal.
2. I don't think it's difficult to use at all and the naming seems logical and straight forward.
3. Please do not use DESCENDANT_ which, while accurate, is too long and something I'd be more likely to misspell. The current naming is fine even if potentially inaccurate.
4. Thanks to the addition of .parse(), nope.
5. I often work with data from outside sources that isn't structured conveniently for my use, so having a locked in XML structure was a bit of overhead that may have been enough to put me off. Now that you have .parse(), I can side step the XML and just throw what's needed into an array and run with it, so I don't have any compelling reason NOT to use LoaderMax.
6. It's simply the convenience of not having to worry about building out a custom loading system for each project. I no longer have to worry about what kinds of things I'm loading or building a system to handle the associated events. Thank you.