The statement “the method is safe for only 5730 years” is incorrect. The half-life is 5,730 years, meaning after one half-life half the original 14C remains; it does not mean the method stops working after that time.
Radiocarbon dating is useful well beyond a single half-life. Modern instrumentation (accelerator mass spectrometry, AMS) and careful sample preparation allow reliable measurements and age estimates out to roughly 40,000–60,000 years, depending on sample quality, contamination, and the lab’s detection limits.
Beyond ~50–60 thousand years the residual 14C becomes extremely small relative to background and contamination, so uncertainties grow and ages become less reliable or are reported as minimum ages.
There are some built in assumptions that determine the outcomes of the readings, and if those assumptions are false, then the readings don't show what people think they show.
One assumption concerns the level of radiation received by the target material, be it a tree, or animal, or whatever, that we "know" what that radiation level was. In fact we do not, as no one was there taking test samples for us. And we have good reason to think it may have been very different.
The Bible addresses this head on:
2 Peter 3:3-7 KJV
3) Knowing this first, that there shall come in the last days scoffers, walking after their own lusts,
4)
And saying, Where is the promise of his coming? for since the fathers fell asleep, all things continue as they were from the beginning of the creation.
5) For this they willingly are ignorant of, that by the word of God the heavens were of old, and the earth standing out of the water and in the water:
6) Whereby the world that then was, being overflowed with water, perished:
7) But the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire against the day of judgment and perdition of ungodly men.
God judged the world once with water, and will again by fire. But people don't want to think about that! So they look at a world ravaged by that flood, that killed all but 8 people, and tell themselves, there wasn't anything cataclysmic, this all happened just like it happens today, over a long long time. In a word, Uniformatarianism.
". . . All things continue as they were from the beginning . . ."
Just like in Romans 1, people did not want to be thankful, and so admit accountability to God, so they chose to forget about Him. Here, they don't want to know God will judge them, again, accountability, so they lie to themselves that
it's all been going on for millions and millions of years, no, this wasn't from God's judgment! Because that would be admitting God will judge me!
Uniformatarianism as a philosophy exists to aid man in ridding God from his thoughts. In fact things have not continued always just as they were. There seem to be no end of "exceptions", such as fossil layers that don't match the theoretical "fossil record", trees standing upright through "millions of years" of rock layers, dinosaur fossils with soft tissue, rocks tested to be millions of years old that were actually formed in the modern day, it goes on and on.
1 Timothy 6:20-21 KJV
20) O Timothy, keep that which is committed to thy trust, avoiding profane and vain babblings, and
oppositions of science falsely so called:
21)
Which some professing have erred concerning the faith. Grace be with thee. Amen.
Much love!