It really depends on each neighborhood these days from what I have seen.
Parks around here, one is safe during the day with many people, it is divided up in many sections well, and you don't notice the drug dealing and needles until the ratio changes after dark.
Most of the other parks, I'd say a majority of women do not feel comfortable, which leads to less use by women and men, which changes the ratio of people that do go there. Some of the parks have been charging and increasing the fees to try to reverse that.
Libraries are the only real bastion of third space that seems to have a mostly neutral vibe imho. Although the downtown libraries have had to change some of what they allow to try to stave off the changing ratio of unshowered, just as several of the starbucks now have number pads on the bathrooms to access.
Libraries are not the best place for socializing as they normally have a keep it quieter vibe in my experience, but it's still doable to meet someone. The lack of open hours is a real limiting factor. I'd like to open a library that is more like a social club and open 24 hours.
Museums have gotten pretty expensive around here, and I don't see them as a great place to socialize. I imagine it's great to bring a family, but replacing the social connect that malls and bars at once had, not really. I also can't imagine people going to the local museum every friday night.