Recently I met a screenwriter who has written a few screenplays but hasn’t sold any (yet!). I asked him about his work–like you do–and he obliged. I found a common theme throughout his work–he had great ideas for worlds and plots, but not such great handle on the “suspension of disbelief” concept. When writing speculative fiction, it’s common for beginners to, for example, use dreams as a gateway to the “other” realm where the story actually takes place, or have characters act in unrealistic ways in order to make the plot work.
Rookie mistakes. I’ve made them, you’ve made them, your friend who has just started writing will make them.
The trick, though, is powering through them and moving past them. Listen to advice. Don’t just get critiques; listen to them and learn from them. Write. Learn. Grow. Repeat.