Not disputing @Toxylon just above, but I’ll call attention to something they said so neatly it might pass unnoticed.
Mom said she’d be considered a failure. IOW, it was others who judged and she felt compulsion to comply with that judgment. Meanwhile, the current generation is deciding for themselves as individuals. That’s a ginormous difference in attitude which leads to an enormous, and much more widely varied range of behaviors by current folks. And not just about marriage.
Moving on to my opinions.
Once one is not forced by social convention or instinctual bio-imperative to reproduce, one doesn’t need a spouse/SO. One might want one, but they come with a lot of disadvantages too.
As a widower in my then-early 60s I definitely saw / see lots of women in similar situations that need a marriage to a man like they need an accordion. Dating is fun; co-habiting is a PITA, and being married means no escape when his / your stuff becomes more than you’re willing to put up with.
See here for more on this from older folk’s POVs:
Taking note of the disastrous baby dearth in many unsettled countries, e.g. Russia, I’m wondering if concerns about global warming, Russian & Chinese aggressions, far-right lunacy in many countries but relevant especially to us here, mostly the US, is leading lots of young folks to say “Baby maybe, but for sure not right now”. Which again really undermines the rationale for committed LTRs versus serial short term “fun in the sun while it lasts” relationships?