If I took snapshots of my psyche every five years for the past 20, what I consider "fun and adventure" would change each time. If I apply that knowledge universally, then I can say what everyone finds fun and adventurous shifts over time whether they're aware of it or not.
What I've also come to realize is that people in general are culturally programmed. When you're very young, and you haven't been exposed to much of anything else, you'll embrace what you're experiencing because your brain wants to absorb all the stimuli it's recieving. Mentally, you're learning what things "should be" or maybe you're learning what they "shouldn't be". Either way you're developing a compass.
By the time your compass is fully developed, times have probably changed, things have shifted, and if they've shifted along a path that's within your adaptive range then you'll be fine with it. If not, then you stop, pause, and say, "Wait a minute..." and start comparing what's new to what you remember.
Once you start looking back to what you were exposed to before, then it's become comfort instead of excitement. So, the question shouldn't be "Is the fun and adventure gone?", it should be "Is the comfort gone?"
Tying it back into the beginning about shifting sense of fun and adventure, experiencing something too many times makes the novelty of something turn stale and stale isn't something that's usually equated with fun and adventure. That's why sequels to movies try to up the ante in each successive installation and when the ante can no longer be topped then they go in a completely different direction. This is one area that benefits TOS since it had a shorter run than any of the others. I'd even say if the other series were like TOS then it would've lost its uniqueness.
If and when there's something wrong with a later series, it's not because of how much it's not like TOS, it's because it either isn't being as faithful to its own premise as it could be or the writing has become stale because epsiodes are being written for the then-current series that could've been done just as easily on one of its predecessors where the only difference is the names are changed.
... and that went a lot longer than I meant.
