Heavy music or progressive music as general cases, are not always appreciated by the masses. 8 minute epics are either for you, or not for you.
I don't agree with that. I like Yes, who has some 20 minute tracks. I love Soft Machine (prog/fusion whatever rock) with many >10 minute tracks. I love King Crimson, that is progressive and sometimes heavy, and has many >8 minute tracks. Voivod and Frank Zappa has some complex songs and definitely not for the masses (except for Frank's parody music stuff). I like early Genesis too. So I can say I love progressive music.
My problem with Tool is not the lengthiness, or epicness itself. Maybe my problem with Tool and similar prog bands is that I feel they are trying too hard to be epic for the epicness, to be complex for the complexness, and progressive for the sake of progressiveness. Plus somehow they perfect the crap their studio albums until they become totally sterile for me.
But it's just my opinion, I just wanted to say that you can't draw any conclusions about someone's taste of music just from him/her not liking a particular (and quite widely known and popular from a genre) band.