Is this a reason why sex has been declining?

Even pre-pandemic that is, for an illustration let’s turn to Washington Post’s Date Lab:

Sam says his ideal partner would share 80 percent of his political views (100 percent “would be boring,” he says), and over the nearly three-hour conversation, they discovered where their 20 percent gap in politics lay: former South Bend, Ind., mayor Pete Buttigieg. When Elli asked him who his preferred candidate was during the 2020 Democratic primaries, she said, “Please don’t say Pete.” (He said Pete.) Sam, on the other hand, says that Elli thought Buttigieg “was a Republican.” Ultimately, it was a difference that both of them could stomach.

Good for them!  They are now set to have an in-person date.