Your recollection makes me wonder if a lot of the old school, unwritten rules about baseball developed out of a culture where players had to police themselves --- just like on the playground. Whereas for over a generation, now, kids learn to play in highly structured environments where childhood rivalry, and the emotional responses they can evoke/provoke, aren't emotions that need to be as developed while playing baseball.
They learn the sport through increasingly structured, safe environments, where those behaviors can be discussed openly with adults and contextualized through the adult lens of competition.
Additionally, however, the younger generation of players grew up in less "safe," environments, or perhaps, less structured spaces, like the classroom/hallways/cafeteria/neighborhood/home, and of course with their online interactions. Online interactions that often include being the target of observation.
I assume that this impacts the generation's willingness to push boundaries/step out of line, both due to the polarizing response demanded by their social networks, but also with an eye toward future royalties earned with having a top-notch K-score*.
The whole generation can "respect" chasing eyeballs with celebrations, while acknowledging that there are still "rules" (e.g. acts of celebration involving teammates are okay, gesturing toward the opposing dugout, not okay). Rules that have been established through learning from the youth levels on.
*Unless you are like Bryson DeChambeau, and your K-score is directly related to challenging convention.