As a junior engineer with only 4 years of experience it is best to take all feedback good and bad to analyze what you may or may not be doing that is not receiving approval acceptable to make it in the production build.
Are you following code style guidelines, is your code secure, is your code fast, are you make large code pushes that takes too long to review and test, are you submitting tests when required, are you updating your documentation, did you follow spec, does your code solve a problem related to a feature, bug request, etc.? If you are then there could be other things that might be outside of what you are doing that are not being properly communicated to you at all.
Have you talked to the team lead about the issues in your code to work towards improving the code you commit? Though it would be very beneficial to have the capability to submit your code to a dev CI/CD system that tells you what is wrong with your code automatically before you submit it for production review.
Though ultimately if you are not receiving feedback on how to improve the code your committing you should bring it up with management as it is the senior and above job to help guide and mentor junior developer's or new team members with any issues in their code. If this is not being done then it could be a leadership, managerial or cultural problem that needs to be resolved early on.
If you are still getting large rejections could you give us a few anonymized samples of some of the rejection notes on your commits?