Earlier quoted context omitted.
I was with you until you said that refraining from hiring someone because his accent was too difficult to understand. That's an insane reason - why pass on a good candidate for this reason? Can your company afford this? If you are working closely with this person, it will be 3 months before his accent is sufficiently adjusted. This is a stupid reason to pass.
I've seen this a million times teaching students. They raise a shitstorm for two weeks because they can't understand their TA's accent. Then they learn and can understand them just fine. The truth is it's part laziness and part racism. That being said, there is reinforcing incentive to be a bad communicator when the people around you don't make the effort because of your accent.
I would lengthen that list to part inexperience, part laziness, part racism, and part a real problem.
College students are one of the stereotypically worst groups for this. They often have only really experienced one accent and racial group - their own. And suddenly they are being taught by people from another country with strong accents. So inexperienced and lazy are likely, while racist is not rare.
By contrast in tech, you have to work with people who have a variety of accents of different kinds and strengths. And frequently this happens over the phone with outsourced teams. The variety is astounding. For example I'm dealing with countries from Paraguay to Vietnam in my co-workers, and regularly deal with have outsourced contractors from India to Poland. I don't have trouble with any of their accents.
When experienced tech people like me give up on trying to understand you, it is unlikely to be inexperience, doubtful to be laziness, and probably isn't racism. Which means that you likely have a real problem.