Half life of c14 is 5,000. It becomes increasingly more difficult to judge decay as time goes on.
The half life of C14 is 5568 years. It’s not more difficult to measure, there’s just less of it — which is why it is a nice way to measure things of organic origin which are younger than 50K years. Not surprisingly, most things that can be carbon-dated don’t reach that age, they vanish.