KayJae, that was my experience exactly!
I went to a conference two years in a row and had the same person in my crit group both times. I really liked her writing, she said positive things about mine, and we decided to exchange MSS by email.
Well, I went first. Ouch.
Here's the thing: most of her points were valid, but the way she said it...
Basically, she told me I had to rewrite the entire plot, especially the beginning and the ending and oh, by the way, even the title won't work. If I'd followed her advice, I'd have ended up with a completely different book from the one I was trying to write. So it made me doubt everything I was trying to accomplish.
Then I worked with a writing coach, and somehow when he made suggestions it felt inspiring, not demoralizing. Like, where the first person said, This is really random, I think you have to make the character do this, the second person said, Tell me why the character is doing this, maybe there's a way to give him a stronger motivation for it.
After his crit, I did a HUGE rewrite, but I did it feeling like, YAY! I can make my story even better! Instead of s**t, I suck, I have to start over.
So now that I'm on the beta coaster again, I'm taking a big step back from all the crits and asking myself, Does that comment fit? Does it help me bring out my vision of this story? Do I agree?
And I try not to take any of it personally.
Ralph Pines, to answer your original question: If you want better response to beta requests, it really helps to build relationships ahead of time by working a lot on SYW and by offering to beta for people. I'm really active in the Children's and Query threads, and I've tried to give a lot of people as much help and feedback as I can. Now when I need betas, a lot of those same people are offering to step up in return. And meanwhile, the process of reading other people's work has taught me so much. It's always easier to see what needs to be fixed when it's someone else's writing and you're not so attached to it.