Hard to comment without seeing your stuff and only hearing your take on the feedback. Post up some samples of your work and I’m sure we can give some honest, constructive criticism.
Feedback from applications may sometimes be specific or general but hard to gauge depending on the firm, your work, the position, etc.
Best is to take feedback with a grain of salt and just work on moving forward. Posting here is a good start. Don’t think of opportunities you missed but those in the future. Learn from feedback and move forward.
R