I think some shows you have to watch at certain ages that align with the characters of the show for them to resonate with you. Once they do, you can carry those memories with you and continue watching those shows many years later.
For example, most adults without young children do not watch kid or teen shows, but you may have fond memories of many kid/teen shows you watched growing up and can still enjoy them today even if they are no longer your first choice to watch of course.
I think it is the same way with non-kid shows like Friends. If you watched Friends during your 20s or 30s, you were probably more inclined to associate with the characters so you were more likely to enjoy it. Trying to watch it for the first time in your 40s or later makes it more difficult to relate to the characters (not impossible of course as some people enjoy it for the first time when they are even older).
At the same time, a lot of shows that I was never interested in when I was younger seem more appealing to me now that I am older.
I am careful to never write off a show due to lack of interest because I know that one day I may find it interesting.
The great thing though is that there are always TV show options available so no matter what you are in the mood to watch, or even rewatch, you always have options to choose from.