I'm usually on the side of agents when it comes to most things, I know so many of them and have a great deal of respect for them.
But.
I really don't like this form rejection on a full thing.
I get that it is done for the same reason that one gets form rejections in general. I also appreciate an agent owes an author nothing. It isn't an agent's job to critique an MS they aren't interested in representing.
All this said, I still feel like it would be nice if, upon reading a full, agents would take a few moments to explain what didn't work for them about the MS. Even if it is as simple to say, "This was a lovely work, but I just didn't connect with it. I can't really explain why, but I think you could easily submit it in its current state without revisions to another agent." Authors can feel as if we are submitting blind. When we get no idea of what we are doing wrong, it's so frustrating. And very difficult to then fix. And considering how few fulls agents request, it isn't like there is the same kind of time constraint as with queries and partials. One also assumes that a request for a full means that the agent saw something professional in the initial query and isn't as concerned about starting a dialogue with a crazy person (another reason for form query rejections).
They aren't under any obligation true, but this is one thing I think would be very helpful if they did.
This and exclusives both bother me.
All that said . . . I'm sorry about your rejections. But on the good side, you are getting requests and that is something to be hugely proud of. Just keep on keeping on. Never give up! Never surrender!