I'm not sure how you found Journey 'flatter' than Flower, especially when talking about gameplay, Journey is much more 'gamey'.
And your argument would put Flower into a 'holding X for 95% percent of the time' game would it not? Stripping any game down to it's basic elements like that does it a massive disservice - especially games like Journey and Flower, which are audiovisual experiences.
I'd say, objectively, Journey offers the possibility of more fun because the depth of gameplay
is more substantial than Flower, and that's a fact.
Journey succeeds in what it seeks to achieve moreso than Ico because it doesn't sacrifice any other elements despite it's achievements (whereas Ico had so-so combat), it's pretty much expertly crafted in every area - shallow gameplay is not a shortcoming for Journey, TGC have stripped away all of the superfluous elements that come with modern day gaming and created a simple yet perfectly designed game. There's nothing more it
needs IMO, the mechanics and the gameplay match the narrative perfectly.
TGC have proved that you don't
need complicated mechanics or various gameplay systems to create an amazing game, it may be short and simple - but Journey offers an emotional thunderstorm of an experience that transcends yet
perfects what it means to be a game. Not only does it deserve to be GOTY but it also pulls the rug out from under everything else that has ten times more 'game' for your money
I'm not saying you can't have your own opinion by the way