Should you? Not using your name.
But I might, if I thought I could make it anonymous and if I thought they'd listen. The problem is that biases are implicit. Most people don't mean to not hire anyone but a certain kind of person, or to make people different than they are unwelcome, or to exclude them. They don't even know they're doing it most of the time, until someone points out something like what you noticed. And when it is pointed out, they can hide behind excuses that try to shift the blame to someone else, usually the kind of people who aren't employed there. It's a lot easier to say everyone who doesn't work there isn't good enough than it is to ask why a whole group of people aren't good enough.
For the obvious reasons, people don't like you for pointing out their biases. If you're on the job hunt, you have good reasons not to say anything. And as other answers have mentioned, it's not your job to fix their hiring practices. But you've observed something that troubles you, and it goes toward the fact that a work place is more than just a place at which you perform work.
Work places have cultures, by which I mean they have expectations, practices, ethics, and rules which are specific to that work place and the people in it. It's those invisible rules that dictate who succeeds in a situation, far more than their individual skills.
The only way to see those rules is to look at something they effect, like who tends to get hired and how long they stay. The rule of thumb here is that if whole groups of people aren't there and/or leave after a short period of time, there's something wrong. Unfortunately, people often stop paying attention when they find something else to blame it on and the cause could be many things, so it can be really challenging to put your finger on why.
Let me put it to you this way: sure, a company full of people who look alike could be a coincidence. It just usually isn't, as any number of studies on bias can tell you.
Think of this as a learning experience--if what you observe during interviews makes you uncomfortable, you've learned the kind of company you don't want to work for and what you're willing to put up with in an employer. Whether or not you have an ethical duty to say something--you'll have to figure that out on your own. My advice would be to be very careful commenting.
But I want to encourage you to take the culture of a work place seriously as you look for a job, as much as you can. A work place with a culture that is uncomfortable for you has a powerful impact on your ability to get work done in it. Trust me, if you're not welcome in a work place, Murphy's law about things going wrong applies at least three times as much as it should: if it can go wrong, it will go wrong. Daily. With fireworks and a three ring circus.
You may not have the luxury of paying attention to all this, but it is something to keep in mind during the job search: the invisible rules matter a lot more than people think they do. And people often put on their best face during an interview.
No situation or work place will be perfect. But if your instincts are telling you there's something there, it's worth paying attention to them--if for no other reason than because it could be a sign that you would not fit in.