11 has artificial hardware requirements built in that will prevent it from installing on a lot of computers (possibly most computers deployed in the world, at this point) which is the main issue. All those non-technical home users who bought a brand name prebuilt PC in 5, 6, however many years ago that still works just fine will not be able to upgrade.
They will be left in the lurch unless M$ relents and removes those requirements (unlikely), they all learn to patch them out themselves (extremely unlikely), or they all go buy new computers with newer hardware (extremely annoying).