Full disclosure: I am not published. I have worked in publishing, but on the textbook end and in sales. The closest I came to any sort of editing was working with acquisitions. So, I don't really know any secret insider information.
But I have a theory about beta readers.
Should your betas be writers? Uh, yeah. Writers are more plugged in to trends in the industry, what's getting picked up right now and what's getting passed over. They are more likely than your sister's best friend from college to catch hackneyed phrases, mistakes, repeats in your MS, etc. They also have an ability to zero in on what isn't working and why.
But in all the time we spend learning about what agents and editors are looking for we get caught up in minutae. We put so much blood, sweat, and tears into trying not to be just another vampire book or cozy mystery or whatever that it screams at us when we see it in an MS. Basically, we fall into the trap of writing for agents.
It makes sense, since most of us won't get published until after we cross that first hurdle. But agents are not your actual market. People who will buy your book for any other reason than they know you, like you, or feel sorry for you want to read a good story. If you are a genre writer, you'd best know what expectations those people have. Odds are good that they do not look for massive doses of originality. Sci Fi readers who like space stories want some cool gadgets. Romance readers want an HEA. (Heck, some of them want as many HEAs set in nineteenth century France as they can get their hands on.) YA readers want to know who to cheer for. Mystery readers want to know who pulled the trigger.
So your authorial beta readers, who are looking for fresh, cool ideas and solid writing, sometimes pay more attention to those things than the story. They get so turned off by something that seems like a cliche that it might kill the whole MS for them. Readers, plain old garden variety, don't care so much. Otherwise, how do you explain John Grisham?
If all your writer friends think you are amazing but nobody normal gets carried away with your MS, then you have an elite but unprofitable target market. Get a couple of people who don't know anything about anything to read your MS and tell you if they like it or hate it. You might have to fish for info, ask specific questions about things you aren't sure work, but their opinion should count because at the end of the day, those are the people who will pay real money for your book.
My personal theory is start with a couple of non-writers you trust to be honest. If they like the story, get some writer betas to help you sand down the rough edges and make it pretty. Then run it by another non-writer (or even one who's already seen it) and see how it plays. That way, you get input on craft and the impact of the story.