I have a litmus strip I use for weeding out people. If I hear the words "I would do" I move on. Not always but 99% of the time. They're not doing it, I am and their "I would do" is quite often at odds of what I want to achieve.
Regarding your beta readers who tear down... is it possible they think that that is what they're supposed to do? Some people don't get that being a beta reader doesn't mean they're the blood hound to find the errors. They should be working toward improving the whole; leaving what is good and/or improving it, and pointing out where improvement is needed.
An example:
Years ago I was hired by a playwright to help her with her play. In it was a monologue (because everyone thinks a play HAS to have a monologue) that was static. It was a long laundry list of things a woman missed having had to flee her country. The monologue was told to her daughter. To this point there were no scenes that conveyed the love that the mother had for her daughter. Just arguments yet the mother would tell other people how much she loved her daughter.
My thought was that she should make the monologue into more of a duet between the two and get some affection going. But... that was how I would do it and I didn't want to say that to her. She recognized that this was a problem area so we discussed it for our whole session, what was lacking how it was presented and yes, I did sneak in my idea. But when she left to work on the play she had a handful of possibilities. Forgive me if I blow my own horn, but she came back and had used my idea but she took it much much further and made it into a new scene between the daughter and mother where they both reminisced, even to the point of playing the piano and dancing. It was a lovely lovely scene, far better than I thought possible.
My point: I could have torn what she wrote down. But there was something there. There was a possibility of so much more and our discussion revealed that. In the end she did it, all by herself. Tearing down just doesn't work.
Go with the people who offer solid help.
Write hard, write true.