Sure, but this is about IP law instead of physical goods.
This is like if you left your door wide open, and a neighbor peaked in and told another neighbor about your decor or what posters are on the walls.
You didn’t lose anything tangible, but something you wanted to be secret isn’t anymore. Where the balance of blame falls is up to you, but I do think to some degree that if you want to keep a secret and can’t put in the bare minimum effort to even try to protect it then you own some of the blame.
There are absolutely laws about IP theft. That's why it's called Intellectual Property.
You really don't want the law to be "Well you didn't lose a physical thing, so why should it be illegal?"
Having access doesn't mean you are allowed to access something. Let's say I started working at a new company and notice I can still access the source code at my old company. This doesn't mean I am allowed to download it and give it to my new employer even if we just use it as a reference.
It's more like if you left your door unlocked, and I hire somebody to break into your house and make copies of documents you left sitting on the counter. They discover that the door is unlocked so their job is real easy, hooray! Doesn't matter, still very illegal, and both I and the person I hired should be prosecuted for it.
The difference is there's no laws around your home decor, but there is a clear legal framework around trade secrets. Apple's allegation is that a vulnerability was exploited to access some of the data as well which, if true, carries potential CFAA criminal charges.
For trade secrets, it only requires "reasonable measures" even just having an NDA is enough, even if the rest of your security is wide open. Just because someone found a loophole or grabbed files before their access was revoked doesn't make it legal (under trade secrets law).
Almost certainly the employees at some point in their tenure at apple signed some duty of confidentiality, or some acceptable use policy, etc. which is grounds enough for illegal misappropriation. "You didn't lock down their access enough" isn't a valid legal defense.