Regnal lists of the Sumerians, Japanese, Chinese, Koreans, Vietnamese, Persians, etc. all have preposterous claims to ages 100+ when you get really far back.
How do historians approach such claims? Are the ages wrong but the people existed? Or are the ages wrong AND the people never existed?
Like, how do scholars view Emperor Jimmu?
There's more to be said on many of the civilizations you mention, but you might be interested in this older answer by u/kookingpot.