If your actual resume consists mostly or exclusively of theoretical future accomplishments, employers will be justified in wondering whether you've actually successfully done anything. If your cover letter consists mostly of rehashing what you've done in the past rather than what you can do in the specific role, employers will be justified in being sceptical about whether you've actually considered whether you're actually the candidate they need.
If your actual resume consists mostly or exclusively of theoretical future accomplishments, employers will be justified in wondering whether you've actually successfully done anything. If your cover letter consists mostly of rehashing what you've done in the past rather than what you can do in the specific role, employers will be justified in being sceptical about whether you've actually considered whether you're actually the candidate they need.