There are many different ways to take the phrase "full featured". Some accept a browser as full featured if it accepts compatible html. Some aren't happy unless it has full emulation of all IE's bugs and useless additions, password managers, flash, obscure javascript commands, java, CSS, and whatever new badly planned and poorly implemented new tricks the internet pull out to attract visitors.
12MB unextracted for a browser is not slim (not even for 2003), especially considering it's basically a glorified text viewer.