Supersystem is about a very different game than the one most posters on this forum play in. That's why it should come with a warning label, just like the "loose games" section in HEPFAP.
Brunson was writing about big-bet games with MUCH deeper stacks than most online games, and was writing at a time when most "strong" players were extremely weak-tight. In games like this (1) the implied odds for hands like suited connectors are much higher and (2) the deeper stacks make strong semibluffs much more powerful and also allow for meaningful betting (and bluffing) on all streets.
I feel like the most common mistakes on this forum come from players who fail to understand the various implications of stack size, both in relation to the blinds and to the sizes of other stacks at the table. About once a month, I post a link to
GoG's post on stack sizes, which I think is a great starting place for players looking to sharpen their understanding of these concepts. There's plenty of great stuff in the archives--just go digging!
scrub