I don't know how well this actually answers your initial question, I think it's more of a counterpoint to some of the stuff people have already said, but here it goes.
In the past (prior to social media or search engines) specific styles, specialized knowledge, and niche awareness actually took effort. You had to go out into the world and find a scene, be accepted, participate in it, contribute to it, and learn from others with specific knowledge within the specific sub- or counter-cultural scene. It took time, effort, and experience to craft an identity. Nowadays people cycle through various identities and trends like commodities because it takes no effort (they're sold to them by social media algorithms, influencers, brand accounts, etc.). It comes to you in your phone without you ever even having to leave the house or put in the time to discover it or participate in it (you just follow specific people or subscribe). You can be a passive observer or consumer, not an active contributor. As a result, you're not invested or tied down and committed to that core identity. You can cosplay depending on your mood or who you want to momentarily convey yourself as, because it's easy. Essentially, being a poser has become normalized. An identity is now something to be momentarily consumed and affected, rather than grown, built, and developed over time.
Granted, it's always been different in regards to "mass" culture and popular trends (both in the past and now). Those are impossible to miss and were always monopolized by specific trend setting institutions, but always by the time it gets to that point, the actual initial counter- or sub-culture that inspired it has already been coopted and has started to disintegrate under the weight and attention of mass consumption.
