Based on the erotic game by ClockUp.

What is it like being an older anime fan, and how do you relate to the younger anime fans?

I have been watching anime for a long time now.
My flavor text states 15 years, but even when counting conservatively, 20 years would probably be closer to the truth now...
as such, I think I am in a fairly good position to answer this. So... What it is like being an older anime fan: Well, let's start with the nice stuff.
First off, you are no longer a penniless student - instead you have a fulltime employment that provides you with hobby pockets way deeper than you would have imagined in your teen days. Meaning that you can not only get your hands on all sorts of flashy merchandise - no, you can actually get on a plane and even visit the actual locations of the titles you love.
Which is amazing.
Few things beat standing in the same places as your dearest characters, and it will give you a whole new level of "locality/sense of being there" when you rewatch that title later. Second, you will have gained a deep and well-reflected knowledge of your own tastes over time (which also are a lot more specific/refined now).
You will now be aware what parts exactly you enjoy about a given anime series, rather than 'simply enjoying it'.
Also, you will be able to put these things into proper words, and know the reasons why you enjoy them. Add to that a high level of expertise when it comes to all things anime.
You will immediately be able to tell a good plot / pacing / design / seiyuu performance / animation quality / etc.
from a bad one.
You will recognize a ton of stylistic, narrative or emotional devices indigenous to anime that most other viewers will not even notice.
Finally, you will also understand the many deliberate tongue-in-cheek references to older stuff that the authors hide in current series. On a less enjoyable note, you will also need that expertise and knowledge of your taste to skillfully pick the right series for you.
Since, when you have seen thousands of titles, the bar for a "good series" will be set very high in your mind. This means that it will now take a lot to make you go "wow!" when watching a new series.
Usually it now relates to things on a smaller scale - for example when you acknowledge a single new innovative (or well-written) character or an emotionally touching / surprising plot twist. Mind, you will still enjoy the various new titles coming out, but actually finding a series that totally blows you away in its entirety becomes increasingly difficult. Finally, as a result of all this expertise and experience, you will notice how your perspective grows more and more "meta".
You will more and more see the "seams" that hold things together.
You will notice and judge their plotwork, their internal continuity, their production values, their chara design decisions...
in short, you will also judge on levels beyond the mere direct, subjective in-your-face experience. In a way, this means that you will be able to take a step back and objectively see titles for what they really are.
Both their strengths and weaknesses. How does one relate to the younger fans: I won't lie, interacting with younger fans does have its challenges.
This holds all the more true the "newer" that fan is.
It requires a conscious effort to constantly put yourself into their shoes, i.e.
to see things with their eyes. When you look at a newly-released title, you see it as an iteration of existing themes that is based on many previous titles from that subgenre (and inevitably measure it up against those).
They on the other hand will see something totally new, groundbreaking and mind-blowing.
And it is - for them. And to understand them, you will need to constantly remind yourself of that fact, and remember how you yourself felt when you faced "your" first major series of that style/genre/philosophy: the intense rush, the unbridled enthusiasm, the feeling of epiphany upon discovering something you had never seen before - and the utter willingness to (and joy of) devoting yourself to it. Along with that aspect, you will have to keep a very tight grip on your language.
As these fans are extremely emotionally invested in their current titles (and often too young to appreciate a dialectic approach), a single wrong word can completely break the conversation: As soon as they get the slightest impression that you might consider "their" title as below-average or even bad, there is a high risk that they will (needlessly) turn defensive, aggressive and irrational. However, as long you keep those two things in mind, there is a lot of good stuff that can come from this veteran/newcomer interaction. For the veteran, it is the opportunity to connect with the fervor of his younger days, and helping a less experienced fan across the various hurdles that stand in his way - so that he can become a veteran some day, thus furthering the overall cause of anime. For the newcomer, it is the opportunity to tap into a vast range of knowledge, ideally providing new options and alternatives that he wasn't even aware of before - thus broadening his view and allowing him to better explore (and ultimately understand) his own tastes. TL;DR: In many ways, the relationship is quite a bit like this one...