Heritage House, Community Center, Town Hall - most towns and cities have groups for the elderly population. We have a church here in town that holds weekly Bingo. One does not have to be a member, but it's a great way to get out and meet other people.
It's hard getting older, it can be very isolating but the steps to remedy that can also seem very overwhelming for people who have been used to their communities being in their neighborhoods. But friends move, kids grow up and move away, so a supplement needs to be found.
Unfortunately, I have no advice for adult children who don't seem to care about abandoning their parents. Some people are just wired differently in that regard. But I can't see a situation where a message of "hey, let's maybe put a little time and effort into our parents who may not be here for that much longer" is positively received. It never was when I tried with my sisters in regard to my dad.
You just have to keep doing the things that bring YOU peace of mind as it relates to the aging parents.