Space Mountain is not a ride for thrill seekers. It has a max speed of 28 mph, 26 ft drop, no inversions, and 3.7 Gs. Any other park would call it a kiddie coaster.
It very much is a ride for thrill seekers. As somebody that loves super intense coasters and goes rock climbing and sky diving (actually sky diving is kind of boring), and heli skiing, etc, Space Mountain is very much able to produce thrill. There is a lot more to thrill than speed and Gs. It's not an intense coaster, but it's certainly a thrilling one.