Imagine you're at a party and someone mentions that they just came back from Paris. Someone else pipes up "oh, I've also visited [place]." How relevant does [place] have to be for you to feel that the response is reasonable?
1) "I've also been Paris!"
2) "I've been to France!"
3) "I once went to Belgium!"
4) "I've been to Greece!"
5) "My cousin went to Greece once..."
A couple of things seem clear to me. First, the relevance of these responses depends partly on your context. If you're in a place where few people have ever visited Europe, a visit to Belgium or Greece is a more-reasonable thing to mention in response to a Paris; meanwhile, if you're in another part of France, replying to someone's trip to Paris by saying "I've been to France!" would just be absurd.
However, while context matters, I notice that individual people have wildly different standards for when an anecdote they want to share is sufficiently relevant to be a valid conversational move. Too many times I have sat in conversations that go like:
A: "I just got back from Nashville!"
Me, in my head: hmm, I once went to Sneedville, but I'm not sure that's relevant enough to mention – it's a totally different part of the state
B, excitedly: "That's so funny! I just watched this movie set in Montgomery, Alabama"
Me: what the ?@3?@£?
Of course, cities are merely a conveniently-literal example of the broader phenomenon: different people have wildly different ideas of how "nearby" (in conceptual space) their response has to be for it to count as relevant to the conversation.
Analogously to the non-interrupter problem, if you have a higher standard for relevance than other people in a group then you will find it hard to get a word in: while you're busy deciding that your interest in classical physics is probably insufficently relevant to mention to the quantum physicist you just met, someone else has already butted in to announce that their cousin studies insects (or was it tigers? haven't seen that cousin in years), and the conversation has moved on.
In fact, one recurring issue is that what seems relevant depends partly on the granularity of your knowledge of a particular area. The less you know about something, the bigger the area of things that seem "roughly similar" to any specific point in it.... so in a group with mixed levels of knowledge, there's a risk of the conversation always getting dominated by the people who have the least granular knowledge. As group size increases, you have a growing probability that the conversation will be dominated entirely by the people who have the least granular map of a given topic, and can therefore jump in fastest with something that (to them) feels "close enough" to the original prompt. (This is one reason why, for example, all conversations around technology right now end up becoming a conversation about chatGPT, no matter how irrelevant chatGPT is to the original topic mentioned).