I loved the game personally and replayed it many times, the story wasn't as great as other Metal Gear games and it was a bit short but as a hack 'n' slash game it'd be slightly annoying if there was 20 minute cut-scenes in-between each stage, the way I see it, it's called Metal Gear RISING not Metal Gear SOLID so it's like a separate series (though is still technically canon, takes place 4 years after MGS4)
More like semi-canon. IIRC, Kojima said MGR:R takes place in an alternate timeline; all the Metal Gear games up to MGS4 (timeline wise) officially happened for MGR:R, but MGR:R won't have happened for any future MGS games taking place after MGS4.
It's kind of like how Nier takes place after the secret ending of Drakengard but Drakengard 2/3 follow a different ending.
I would like you to provide a post-release link that confirms that it is non-canon, as you seem to be making a very common mistake in reading Kojima saying once that it wasn't what he personally would have done as "I will ignore this." He has said he let the other members of KojiPro handle all the story stuff and that he respects their decisions. Together, it has been stated numerous times that it IS canon and that the only complaint Platinum had was being restricted, somewhat by the lore. The ONLY time anyone said it even might have been an alternate timeline was in a mistranslated Kojima interview, back before it was confirmed to, indeed, be canon.