All Catholics are responsible for building a community within our church. Parish coffee hour is the ideal place to start. U.S. Catholic had an article by Molly Jo Rose about the value of coffee hour after Mass. She's an advocate and she gives many good points.
However, being an old grouch, I would never go. Well, maybe I would if I had a young family and the kids wanted to go, but I don't think we'd have had time. Sundays we went to grandma's for breakfast and everyone enjoyed that and would have hated to miss it.
But if that weren't the case? Nah!
They'd probably be hockey practice, or some other sport to go to. IOW, Sundays were always family fun times.
I think post Mass coffee hour works in Protestant Churches because they only have one or two services on Sundays. We have Masses Saturday evenings and Sunday mornings. We don't usually go to the same Mass, every Sunday, because one of the kids was an acolyte and we went to the Mass she was assigned to.
BTW, that's the best way to get to know your parish. Join choir, CYO basketball or other kids' sports, teach faith formation, prayer shawl, St. Vincent de Paul or Holy Name, etc. The parish doesn't have anything for you? Good, they need you. You start something.
In fact, start a parish welcome wagon. When someone new registers in the parish, give them a call and see if you can come over to their home and welcome them to the parish and talk about their new faith community. Bring little samples from local businesses and pamphlets, school information, doctors, hospitals, etc.