I started playing Minecraft in 2012, on version 1.3. That was ten years ago now but still a lot further along than the Beta versions. Today I play mostly 1.14, which is way newer but still about 4 years old. What do you think should be the cutoff between the different “eras” of MC?
The definition will always be changing, because all versions of the game are always getting older.
1.20 was just released, but in a decade it will feel nostalgic to many.