I can't know precisely how good of a filter it is but I'm not interested in finding out a definite figure.
I have read enough great stuff from picking up a book from 300 BCE or so and I've seen enough BS ghost written flavor of the month non-fiction to know it's good enough heuristics to suggest it in this forum.
A filter can be good in a couple of ways: it can filter out ~all of what you don't want, and/or ~none of what you do want.
Time is a good filter in the first way, which makes it a good filter. Because a filter which doesn't substantially do the first of these things isn't actually filtering: the null filter filters none of what you do want, by failing to reduce the data stream in any way.
I have read enough great stuff from picking up a book from 300 BCE or so and I've seen enough BS ghost written flavor of the month non-fiction to know it's good enough heuristics to suggest it in this forum.