The value of honest, engaged, and committed alpha and beta readers cannot be overestimated. If you're lucky, they are reader, proofreader, and editor, all rolled into one... like mine. They help you keep on track, make sense of muddled thinking, and tell you where there are blanks you forgot to fill in. The red pen becomes something you look forward to, if you're like me, because I know they are helping me put forward the very best version of my story that I possibly can, just as my editor does.
The other value of that red pen is when they react to the writing. The "OMG, yes!" responses make me happy, because these are the earliest reviews, the earliest squirms-in-the-seat reactions, and the earliest rave (or less than rave) responses. But the 'awkward wording' and the 'this doesn't make sense' responses make me even happier, because those help me hone my craft and polish my writing. They mean even more than the praise, at these early stages.
So, here's to the alpha and beta readers in our writing lives, whose red pens and "OMGs" keep us going, keep us writing, and keep us writing well!