In order for a layer of material to be deposited, something has to be beneath it to support it.
It can't float in mid-air, particularly if the material involved is sand, mud, or molten rock.
I thought it would be useful to present an example where the geology is simple, and unsurprisingly, the method does work well, to show the quality of data that would have to be invalidated before a major revision of the geologic time scale could be accepted by conventional scientists.
There are situations where it potentially fails -- for example, in cave deposits.
A common form of criticism is to cite geologically complicated situations where the application of radiometric dating is very challenging.
These are often characterised as the norm, rather than the exception.
Fundamental to stratigraphy are a set of simple principles, based on elementary geometry, empirical observation of the way these rocks are deposited today, and gravity.
Most of these principles were formally proposed by Nicolaus Steno (Niels Steensen, Danish), in 1669, although some have an even older heritage that extends as far back as the authors of the Bible.