These are all great points and point at something which is unfortunately a difficult barrier to cross - one of culture. Older folks aren't used to doing these, and so many of them end up being resistant. They then realize that their social lives are lacking, and lament not being in the office if they don't otherwise have good social connections outside of the office. It's nice to hear that your work gave it a shot, and it sucks to hear that none of these caught on. I personally have an extremely active social life outside of work, so I've never enjoyed too much small talk or getting to know my coworkers on too deep of a level, but I definitely see many of my fellow coworkers and acquaintances struggling with this kind of problem. As I said before, I think you need to keep opening doors to see which ones work. Which doors work will vary from person to person, and as you likely have already noticed the people who start random conversations on slack are likely the same small group of individuals and it's rough to try and get people who don't normally interact to actually interact.

Hopefully something from the reply ended up being helpful to you to start thinking about the process. As an aside, here's a short list of some questions that are a little bit more personal/substantial than small talk, but are great once you've established a foothold to start to get to know someone and build some trust:

• If you were going about your normal day, how many owls would you need to see before you thought something was wrong?
• What’s one thing you’ve changed your mind about over the last year and why?
• If you could share one of your memories with anyone you wanted to, & they would get to experience it just like you did, which memory would you share?
• If you had a box full of all the lost items from throughout your life, what would be the first item you look for?
• If I were to lose all memory, what is the first thing you’d tell me about us?
• Who the most intelligent or interesting person that you've personally known?
• What’s something you hate that you wish that you loved?