Well, I am one of the many people who theoretically can hack someone's system while not leaving evidences of it, at least not evidences pointing to myself.
I do have people I dislike, and yet I don't hack in their systems to plant false evidences.
If you want to get back at someone, you could just punch them in the face or kick them in the nuts. We live in a world where simple assault results in less serious consequences than hacking.
While I am sure you are competent like most folks on here, I will say this: I have met a good number of people who claim they can "get in and get out un-noticed". In retrospect, I think rarely did they consider the possibilities of observation beyond the actual target system.
My point is this: There is no defense against 0-day/X-day exploits in the wild. But the second best thing against being patched is logging and properly tuned alerting. In my 20-ish years of working in this field I've caught half a dozen attackers/intruders via logs and anomaly alerts. Without those 2nd best things in place the entire network(s) would probably have been compromised.
Some crimes are trivial to commit. Walking away unscathed from committing the crime is far harder than one might think. Consequences are inevitable, one way or another.
I do have people I dislike, and yet I don't hack in their systems to plant false evidences.