So you could also do without the majority of Ravel, some Debussy, Copland, Prokofiev, Shostakovich and undoubtedly others?
Don't even bother with Thierry; he's a smug little b*tch who hates jazz musicians for reasons that can't possibly be explained with rationality or good sense. He's likely a f**king closet racist also, since he's willing to completely discount jazz's harmonic innovations and cultural importance (more akin to 'It's only good if some European white guy scrawled it on a piece of manuscript paper.'). Don't waste your breath.
As for bands that don't do things in the safe and formulaic way Dream Theater does, have we forgotten acts like the Beatles, Queen, Yes, Billy Joel, Elton John, maybe Radiohead, Soundgarden, and more recently Dillinger Escape Plan, SiKth, and loads of other underground acts who don't get their balls fondled as much as prog metal acts. To me, Dream Theater plays very well, but their compositions and, worse yet, their lyrics, just don't sparkle with any originality or semblance of risk-taking. They've found a creative comfort zone and they're guilty of wallowing in it, instead of trying to be expansive, or as the case may be, 'progressive'. They draw way too blatently off of other bands' styles, ranging from Queenscryche to Tool to Metallica to Pink Floyd. They know that their fans are dedicated enough to keep buying their albums as long as they have the stock Dream Theater staples (double-bass runs, rip-roaring solos, 10 minute track lengths, cheesy artwork) and frankly, it's become BORING and shallow.
Rock music is certainly not something I've ever discounted, but bands like Dream Theater, Dragon Force, and Symphony X show me just how bad things can get if a bunch of people never learn to listen to other kinds of music, i.e. experience that helps one return to rock music with a perspective based on expectations beyond the gaudy excess and hollow content of stadium-tested garbage.