I've had a couple of beta readers who've gone further with the criticism and I'm making a point now to tell my betas that I'm fine with it to hopefully combat that fear of upsetting me. And as you say, some people are very good at giving useful critique, so I want to keep building beta relationships with people who have done that for me in the past.

It's definitely scary asking for some I admire to look at my work, but I think it'll be worth it. I was actually thinking about doing that with the fic I'm currently working on as I writer I really admire expressed interest in it when I first picked the prompt, so I'll have to gather up my courage and ask if they're open to reading through it!