We will deal with carbon dating first and then with the other dating methods.Carbon has unique properties that are essential for life on Earth.
The strength of the Earth's magnetic field affects the amount of cosmic rays entering the atmosphere.
A stronger magnetic field deflects more cosmic rays away from the Earth.
So, we have a “clock” which starts ticking the moment something dies.
Obviously, this works only for things which were once living.
Also, the Genesis flood would have greatly upset the carbon balance.
The flood buried a huge amount of carbon, which became coal, oil, etc., lowering the total C ratio in plants/animals/the atmosphere before the flood had to be lower than what it is now.
These techniques, unlike carbon dating, mostly use the relative concentrations of parent and daughter products in radioactive decay chains.
For example, potassium-40 decays to argon-40; uranium-238 decays to lead-206 via other elements like radium; uranium-235 decays to lead-207; rubidium-87 decays to strontium-87; etc.
When a “date” differs from that expected, researchers readily invent excuses for rejecting the result.