As someone whose favourite characters in Hetalia are all pretty fleshed out in the manga, I get confused when people say canon didn't give us much, but to be fair, there are plenty of characters that didn't get fleshed out since there are so many, so it really just depends who you're talking about.
I'm someone who enjoys a lot of canon and then completely revises other parts of it. I often enjoy canon when it comes to my favourite characters, and I tend to come up with ideas for them that turn out to be canon. Then there are characters who I want to like because I feel they have potential, but I don't care for their portrayal or there isn't enough of them and I change them up or add new things.
I don't think it's necessary to fully abandon canon (unless you want to) nor do I think it's necessary to follow it completely.
