@dad
You seemed to be focusing on the limitation of radiocarbon isotopes (C-14) for radiometric dating methods, and ignoring methods of other isotopes that can be used.
By using other isotopes you can determine how accurate or inaccurate C-14 method is, especially dealing with false reading that old carbon might give. By using these other methods and targeting at different isotopes, you can compare these methods, to find more precise dates.
@ChristineM have already shared a list of some of radioactive isotopes and their respective half-lives, but there are lot more isotopes that ChristineM haven’t shown. Such as K-Ar method potassium K-40 1.24, argon Ar-40. The lead to lead (Pb-Pb) dating have been used to date certain types of meteorites, as well as the age of the Earth. The only other method capable of measuring the age of the Earth is U-Pb method.
Some of the oldest objects in the Solar System are planetesimals, like asteroids and meteorite, because these objects haven’t undergone much changes (such as melting) since the formation of the Earth, and the interiors of meteorites would not have been contaminated by the Earth’s environments.
Also, other modern dating techniques can be used to date the layers of where remains, fossils or other artifacts were buried, that don’t use radiometric methods; these techniques are known as luminescence dating.
Basically they would date specific minerals (eg potassium feldspar, quartz) that have been sufficiently bleached by sunlight, before they are buried. Soil, sands and sedimentary rocks would contain trace elements of radioactive isotopes. Specialists would either use light, infrared or heat, depending on mineral types, to release any unstable trapped electrons in objects and measure the age, since the objects have been buried.
For quartz, either blue or green light can be used, this method is known as optical stimulated luminescence (OSL). OSL can measure any objects containing quartz, from 100 years to about 300,000 years.
While the infrared technique is called infrared stimulated luminescence (IRSL), can be used on any potassium feldspar minerals, which are commonly found in clay minerals. Since IRSL measure any clay minerals, therefore it is most useful in dating pottery and ceramic wares. The limit to IRSL is about 1 million year.
The other luminescence technique that doesn’t use light, but use heat to release unstable trapped electrons is thermoluminescence (TL). TL can measure any minerals, just as well as OSL & IRSL, but focused on objects that have been burned, like fired pottery.
Any of these techniques can be used not only the last 1 million years on rocks, but also archaeological objects, so it can date human activities, such as pottery, tombs or burials. All those luminescence techniques don’t suffer from false ages that occasionally contaminated with readings of radiocarbon dating.
Luminescence dating can confirm any radiometric dating methods in human history, which is what is needed for age verification.