I don't agree with the author's claim that "Gone Home" is 'not a game,' and especially not with his apparent belief that it's obvious that his opinion is correc

I don't agree with the author's claim that "Gone Home" is 'not a game,' and especially not with his apparent belief that it's obvious that his opinion is correct. But I don't see the point of prefacing things with "in my opinion." I thought that was generally assumed wherever applicable.