They are honestly surprised about this in "How To Train Your Dragon"?
The SAME series where they built up how great and strong a Warrior Astrid was, how her entire life is dedicated to being a strong warrior, and how much of a big deal it all ways.
Just for her ONLY contribution to the climax being a "Buck up love interest" and then proceed to be useless contributing absolutely nothing and needing to be saved? Trust me the Mother got more dignity then Astrid did. If Astrid actually became a Warrior in the final scene it would be fine, I mean I understand hiccup needs to be the big dang hero and as such Astrid cannot defeat the big dragon, but is it so bad for her to have given it her all, done amazingly, failed... but gave Hiccup the idea or opening he needed? Or heck have her do something completely different, either way her "Become a warrior" plot just stops because it interferes with Hiccup's.
Also I don't think we are "losing female characters to trinity syndrome", but that is just hyperbole to drive up the view count.
But yes I agree with the actual sentiment of the article (and not the stuff made to increase view count). That just because you have a butt kicking female in your story, it doesn't mean you are prominently featuring a strong female character.
(Also yeah... Lets just say I didn't like "How to Train Your Dragon", its treatment of Astrid was what made me dislike it)