I get that the environmental impacts are pretty significant. I looked it up and it seems like aviation is like ~3% of worldwide emissions and while that’s not really the biggest number I’ve ever seen, it is pretty significant.
I just think it’s equally unreasonable to condemn air travel in general when the alternatives are equally unreasonable. If somebody wants to go on a trip, what should they do? Months-long zero-emission backpacking journey? Never visit anywhere your whole life? Wait for your country to build high speed rail?

https://pmc.ncbi.nlm.nih.gov/articles/PMC8847607/
It’s not just divorce, there’s a variety of factors that are correlated with decision to cohabit. This article goes through a bunch, including for example, martial satisfaction (they call it “adjustment” in this paper) which in their sample was slightly lower in men who cohabit before marriage and a lot lower in women who cohabit before marriage. They don’t really speculate on the reasons for this, but I’ve heard it suggested that cohabitation increases marriages out of convenience among couples who probably wouldn’t have gotten married otherwise.
Also important is that these impacts are long-term, and both cohabitation and marriage have positive outcomes in the short-term.