You may want to tell some of those nosy nellies that the new trend is that middle-aged and older women who are divorced or widowed don't want to get married again, by and large. Most of them want the greater independence and autonomy that was lost to them when they bought into marriage and many of the expectations that go with it. They fell for the societal expectations the first time and discovered it wasn't necessarily all it was cracked up to be.
Can people (particularly women) create truly equitable relationships where they don't lose themselves in the process? I suppose so, but it doesn't happen very often. I'm in a very good marriage but I'm still working to truly reclaim myself after so many years of motherhood and coupledom. Yes, we are social creatures but as you've said, most of this is a story that you can't be happy without a wedding and motherhood. Many of these "not getting married again" women are in relationships, but ones where they still have their own place, and most of the say-so about their lives.
My pretty conventional mother even did this after my dad passed away. She was in another relationship for 22 years but they never lived together or seriously contemplated getting married because she didn't want to. This really is becoming the new trend. The other thing is just an old cultural narrative.
Keep being you!