For me, one of the hardest parts is finding the right music for each scene. Making it feel immersive and match the mood of the moment takes a lot of trial and error. Sometimes a track sounds good on its own, but once it's in the game it just doesn't feel right.
Well, this is a common problem devs encounter because, when you're in charge of the music, the question is not "You like this?". Taste is absolutely subjective, and there's a TON of music that you might like, but at the end of the day, the game is the one who makes the talking.
The real question is, "Does this work for what I'm trying to achieve?" and that usually leads to an answer you might not like.
Devs that don't have a composer needs to think in terms of music functionality instead of taste. And even if you have a composer, this one needs to work the same way. If your composer says "You like this?", then probably is not a good composer.
Also there is a lot of trial and error if you're doing this on your one. That's why composing requires first playing the game, understanding everything around it and THEN making the music.