Both the stories of Radiant Dawn and Conquest weren't very well done, but the gameplay was awesome. Isn't that all that matters in the end?
To play defense for Corrin because I can, we have to remember (and forgive me if I repeated some points earlier):
1. He doesn't have a clue how the real world works. He's been living in a castle by himself and nobody to interact with outside the servants and family. I fully expected terrible decision making.
2. He hasn't been outside, and just learns all these things about him and just has...events happen to him. All within the span of a couple of days, I'd also not expect great decision making either.
3. On top of all that, we can mostly blame Azura for being one of the worst written characters in Fire Emblem history. She...withholds information when not necessary, does that stupid crystal thing, etc.
4. Mildly off topic: People critique Xander for following his father blindly, but if your father went from loving to evil, you'd likely not accept it either. Seeing all his family following his father, it would make sense for Corrin to do the same.