1.) If you spend some time on the site, you'll sooner or later find some new music related to the stuff you already listen to. That happend to me two days after I signed up for it.
yeah it's not that useful for people without a broaden horizon of musical taste. but it looks like you are (still) misinformed about the radio.
what you are talking about is only a feature introduced very recently (neighbour radio). main attribute is you can put your own playlist together based on tags and similarartists. which means it's only YOU that decides what you listen to. though multiple tags and artists combined together just started to be supported since the recent release of the new player.
i like lots of different genres but still i mostly tune in downtempo or triphop on my lastfmplayer :)
but i will stop here as you obviously talk about stuff you have no idea of P