Yes, of course it’s (largely) subjective. But I have actually read much of the source code of Spring. I know it _very_ well.
Anyway, I just wanted to say, that it's totally pointless to state something like "I know it well"... Say what's your problem with it, "I don't like it" doesn't add anything to the conversation. I'm quite sure whatever you would say as problems, most people would agree, maybe there would be even tips under it how to prevent it. That will never happen with the kind of comments which you made above.