Questions: Entertainment & Arts

I want to preface this by saying I apologise for any poor wording, it's not easy for me to put the right words in places for stuff like this. I'm sorry about the rambling in the question.

I'm someone who loves to read and I've always normally been excited to see film and TV adaptions but often they always fail to live up to the mark either the characters don't match the description, they have the wrong personality or they cut good events and make up new ones.

I guess the easiest example is the new Percy Jackson series being made. I really struggle to see Percy and Annabeth in the characters as they don't match the description. I know they are both very good at acting and have a lot of talent but I can never see the character in them, as I always have been able to picture things quite well from a description. I'm curious if this is common?

I'd also like to know your thoughts on if it's okay to struggle with this. As really at the current time it feels like it's not something you can think.

I really hope I've made sense and would really like to know people's thoughts on this, I am once again sorry for any poor wording or rambling.

Role-playing game, not rocket-propelled grenade.