Kaylinn and travelgal - I'm sorry to hear you've had poor luck with beta readers. I think we all must, though. It can take a while to find a good fit. That's been my experience anyway, and I've seen plenty of people say the same. It's been a slow, roundabout course for me, partly due to the fact that I've been finding my niche as a writer all this time, too.
ETA: I just realized, the following may not apply if you really don't have time to read for others, so I apologize. Not meaning to be insensitive. But for others looking for betas:
As far as readers flaking out on you, my best luck with beta readers has come from people who also needed their MS beta'd at the same time. Still, there are always going to be people who don't come through. Usually that's been due to their life blowing up in some way, loss of job, divorce, etc. And I once flaked out on a writer, too - life got super busy suddenly and I had to tell them I didn't know when I'd be able to finish. But in that case, they weren't also reading for me, so at least it wasn't lopsided.
I do think it's important to find betas whose work and skill level is about at the same place as yours, if you're exchanging manuscripts; otherwise, they may be unhappy if yours is in a rougher state. But I've seen in those "find-a-critique-partner" communities people say upfront, 'this is an early draft' kind of thing, so it might be worth a shot to do the same.
Another important things about finding betas: While family and friends can read your work and be supportive (sometimes), they're not usually that helpful in terms of improving your craft. Instead, seek out writers or are writing - or who at least frequently read - the genre and age category (YA) you're writing. It makes a big difference as to how on-point their feedback will be, but perhaps even more importantly, it will give you greater confidence in how seriously to take their feedback.
Finally, Kaylinn, remember to be gentle on yourself. You've had a young child for the past year. That's a really hard time to concentrate on anything. I gave up trying to write during that time, and now I wish I'd tried harder, so even the little you're doing is more than I felt up to. At some point, you'll regain momentum. And even if you set it aside now, this favorite project of yours could still end up being the one you query first. However, I think it's also best to not fixate on things happening a certain way - to give our dreams the freedom to take on new shapes, to be flexible where we don't have total control. I'm an idealist, too, and can relate to much of what you said in your post. My life is very good compared to most of the world, I suspect, but I had romantic visions of saving the world through activism/charitable work, etc., and I found the world is a stubborn thing to change lol. I regret not being a little more selfish and making time for the only thing I've always wanted to do - write fiction - so now I'm passionate about putting my energy into my writing instead.
Sage - It sounds to me like the person with the wrong attitude is your PT. Yikes. I don't like that she thought she had to mention the girl at the front desk's issue with you. Sounds like she may have boundary/control issues.
jtrylch - I didn't realize you were revising between sub rounds. I'm glad you seem to be having constructive conversations with your agent. That's how it's supposed to work.