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The nostalgia. The memories of "bright things" evoke strong, relatable emotions.
The "tension" of the narrative is one of "then" and "now", what was and what is, the memories of the past and the reality of the present, and how the two differ. You took a self-reflective approach to this narrative, so the conflict present was internal, as you reminisced about the days gone by and compared them against the present in a conversation with yourself.
You purposefully do not give names to the friends who are the subjects of the narrative. Nor do you give insight into how the bright things have faded beyond just the exposure to the cruel nature of life and reality, but I think that this is fine. Part of what makes stories so interesting is that they do not spell every little detail out, spoon feeding the reading a constructed message. I have a sense that little everyday things, like sharing jokes and experiences, along with the ability to listen, is what makes the friendship tick. So no, I don't think you need to develop your characters more.
Keep up the reflective, thoughtful writing! Continue to think of little things that make friendships so lasting. You already have great examples in the narrative, and you could even think of more. Find a tiny detail, like the way a friend laughs, and put it under a microscope, giving a seemingly minor thing much more importance. Also, continue to think about the idea of language not adequately summarizing human thought. It's an interesting topic that you could definitely write other pieces on.
Your reflective and compelling narrative packed an emotional punch that had me wishing that "I could turn back time to the good old days" to quote 21 Pilots. Great work!