>Totally makes sense why we'd basically always want someone who has done the trip before. I wonder if that was actually the thought process?

Yes. Besides the shuttle flight denvercoder9 mentioned,[1] there was one Skylab mission with all-rookie astronauts, and a few Gemini two-man flights. So one shuttle flight out of 135, and about four other NASA missions before that. (Obviously I'm excluding the six Mercury one-man flights that were by definition flown by rookies.) NASA always prefers having the commander (the actual pilot), at least, to have flown in space before. The upcoming Crew-3 is unusual in having a rookie commander, but at least the pilot (i.e., copilot) has flown in space before.

This is why NASA has always chosen people with very high-performance aircraft experience as pilot astronauts; it's the best known way to predict beforehand how someone will do at piloting spacecraft, an inherently dangerous and high-stress environment with complex tasks.

Most of the recent news coverage over the "Mercury 13" was nonsense, but especially the stuff about how the women who participated in that endeavor were "trained as NASA astronauts" or "qualified as NASA astronauts". NASA didn't restrict the selection process for the Mercury 7 to exclude women, but to select the best from the US's pool of active-duty military fixed-wing pilots who had graduated from test pilot school. Yes, no women had attended test pilot schools or flew combat military aircraft, but neither did the vast majority of its soldiers, military officers, or even military pilot officers. (Army, too. There has never been a US Army pilot astronaut,[2] and the first Army mission specialists wasn't selected until 1978.)

[1] And even here, Joe Engle was a NASA rookie but had flown to space on the X-15

[2] The most unrealistic part of I Dream of Jeannie is Roger Healey as a 1960s NASA astronaut who is an Army officer