They do seem to support older browsers: just as loadable modules. I am not opposed to the idea that the library runs different code on different browsers to get the job done if I get the same result and a performance gain out. On the other hand it's not code that I would want to debug.

It depends what your writing, and your target market. Most people using webapps/modern websites are doing so with good recent browsers.

[citation needed]

Are you related to the project somehow? You seem to be vigorously defending it, but I see no affiliation mentioned (and your profile here is blank).

How is my above comment defending it? :/ I actually extremely rarely use any js libs. I'd rather just do it myself. And no I'm nothing to do with the project.