the meme was always about millennials feeling old and calling themselves boomers since they associate the boomer term with old people.
also see
>>25353generational identity was largely invented in the 20th century by marketers. tell people that they have a certain identity, tell them that consuming certain products is a way of expressing that identity, sales go up.
before that, generations (just like time in general) were seen as more cyclical. differences were made between people in different age ranges, but there was also a wide belief that people's lives were the same regardless of which "generation" they belonged to