>You only need to be slightly more intelligent than the people trying to track you in order to not get caught. I heard and read enough true crime stories to noticed that successful serial killers and incompetent law enforcement tend to go hand-in-hand.

There is a caveat to this. As the perpetrator of a crime (what and how stuff is defined as a "crime" is a different discussion), no matter how smart you (think) you are, you have to get it right every single time, in perpetuity

For law "enforcement", they only need to get it right once.

No, you have to be more intelligent than anyone who is ever going to investigate you, because any traces you left behind at any point could lead back to you.

When you're doing low-level crime barely on anyone's radar, this matters little. But if you ever scale up, any mistake you may have made in the past could be used against you in the future.

I would guess that things like search history, email records, cell phone records and security cameras are a huge crutch for police these days. So avoiding those things probably gets you most of the way there.

License plates, CCTV, purchase records, public transport etc.

There are so many ways in which you could be tracked that the safe assumption is that you won't be able to avoid it.

Which brings you back to asking why half don't get solved, I suppose.

In most countries: priorities.

" So avoiding those things probably gets you most of the way there."

How do I get anonymous internet access, from inside my cave?

More serious, the "best" way to do crime, is probably doing crime no one (in your jurisdiction) bothers enough to demand police action.

Which is why most(?) cyber gangs are operating from russia, kasachstan, etc. against the west.

Also your list misses IP logging from ISPs.

Uh, meaning don't discuss your crime, search for crime related things, etc, on your phone or home pc, etc. Not living in a cave.