When I watch anime these days I'm usually going back to 1980s/1990s OVAs that I've not seen before or haven't seen in decades. I'm willing to overlook the far-less-polished animation in exchange for interesting stories about adult characters facing adult problems (in the sense of "problems that happen to people over 18"). And there's often some really great high-concept stories that aren't as common in other types of media before or since.

Of course if someone has suggestions for any modern series that lack teens as main characters, I'd be open to watching those as well.