I think the young earthers get God’s covenent with the Israelites confused with the creation of earth. There is plenty of evidence of life and human life well, well, well beyond 6,000 years, though the Jewish story may well have begun around then.
Any serious studier of the Hebrew calendar rapidly learns that dates prior to the Second Temple become exponentially more like suggestions than dates one can compare to some fixed epoch down the the milisecond like we do today.
Back then, calendars were for planting crops, honoring G-d, and jubeliee years. More than 7-8 years was ancient history.
I am not a “young earther”, but I do believe in creationism and think inter-species evolutionism is a fairy tale, which is why after all of these years, evolutionism is nothing more than a theory and can’t be proven (albeit it is a constantly changing theory).