Sometimes it's not the board, that changes, sometimes it's us. It's like in real life. Sometimes things change, sometimes we move in different directions one day. We can't always blame the others.
I know exactly what you feel from another board. I have basically grown up in message boards. They are not the same they used to be anymore.
Every era has an ending. I don't think it's the new users. It's old users growing up and maybe finding a better, another place.
Every community dies out in the end. And then what felt like home once, isn't home anymore. As sad as it is.