"...why not simply say that some characters are polarizing while others are boring?"

Because A) it's not that "simple," and B) it's not an either/or proposition.

Yes there are "boring" HGs. Jessie is boring as heck. If Elissa was not Rachel's sister she's be boring too (except when doing her Yoga of course.)

Jeremy was definitely polarizing. Historically other characters were polarizing also ( i.e. ED, Jase, and Lydia & Ronnie the Rat from BB11 to name a few.)

But SO many HGs (past and present) do not fall into either category. It's not that cut and dry.

Cases in point:

I think Helen is playing the best game thus far. My only criticism is the power may be going to her head and she might be playing too hard now, but hey...at least she's playing! So I would not say she's "boring" OR "polarizing."

Ho-manda is McCrea's skanky whore. Is that boring? No. Is it polarizing? No. It's...well...being a skanky ho. And apparently a fair share of America share my assessment otherwise she would not be America's MVP nominee.

My point being "bell-curve" (love'em or hate'em) is just ONE of many ways to assess a HG in the game of BB. Other ways would include boring or polarizing (just as you stated) as well as, skanky, proactive player who gives 100%, etc., etc.