[commandlinefan]

Actually, I think that's the reason people build new date pickers (or new anything else). The new (fill in the blank) to rule them all has to take every possible permutation of use cases into account, and as a result, is necessarily "bloated" for whatever purpose you intend to put it to. In most cases, it's not just bloated itself, it also depends on other (fill in the blank)s to rule them all that are themselves bloated, and inconsistently compatible. It's also necessarily way more complex than just annotating an HTML input form element - again because of the huge number of different cases it has to support, so take a while to learn how to use and to learn its own idiosyncrasies.