And once you do unlock everything, that's when it's time to start playing other people; then the real fun begins.
While I can agree with online being very... limited, imagine how brawl'd be WITHOUT online at all, for some people. Not everyone has a lot of other people to play with all the time (I live in the middle of nowhere, practically, so... yeah), and you can get sick of the same people over and over too. Online brings a lot of Smash Bros.; be it bare-bones (taken from Bio :P) or not.
... ... ... I'd moap around forever if HG/SS turned out to suck. I've been waiting for a GSC remake for so long... just as we've all been! DX
Also, for sake of mention, my wi-fi barely lags at all, maybe 5% of the time; and that's only on Basic Brawl. As long as you add people in the same area as you (and if you have a good connection, in the same country), you won't be getting lag very often. There's also plenty of ways to prevent lag. Shut down all IE windows on the PC, temporarily, move your signal closer to your Wii and vice versa, etc. etc.