I don't think it's being rude. It's that 20 - 30 years ago, all executives had secretaries who would be tasked with responding to resumes. Now, communication is so easy that nobody needs their own secretary, but the executive is less likely to respond to every resume.
Also, the number of applicants has greatly increased because communication is so much easier, which greatly increases the pain factor trying to respond.
Also, the number of applicants has greatly increased because communication is so much easier, which greatly increases the pain factor trying to respond.