I very much agree with all of this but do you find your friends reciprocate? Also mid 30s, I keep in touch with a few friends but arguably only 1 or 2 consistently reach out on their own.
There were cases where the lack of reciprocation was their way of telling me they were done with the friendship, and so it ended. That happens. Happened to me about 5 times.
But there were a lot of others who were just bad at it or distracted and just needed time and needed me to be patient and not hold it against them, and who came back strongly later on.
There was one who I could tell would never change, who just didn't care and didn't know how to be a good friend, and in their case I slowly stopped reciprocating myself and replied less and less until eventually it was just dead by natural causes, me having accepted the loss of the person I wished they were.
And lastly there was one who was going through such a bad time that they kept pushing everyone away during that period, and in the end they overdosed and died. I wish I had done more, even though I tried actively - I could have tried even harder.
I think it just takes life experience to tell the different cases apart without the benefit of hindsight. Life experience and charitable assumptions.
OTOH, when I see these people after years, it's like no time has passed. OTOOH, in order to be friendly, I have to overcome my general annoyance with their lack of effort.
The friends that make 0 effort however I cut out. You gotta give me something to work with...