On the last days of each of their guest hosting stints, Anderson Cooper and Bill Whitaker both said something like
Alex [Trebek] made hosting Jeopardy! look easy, but it's not.
I'm sure it's a little harder than most other game shows, because the host has to recite all the questions quickly after they're revealed, and some of them can have complex words or phrases. But what else do they have to do that would make it difficult? They're not judging the players' answers, there are judges for that. Both Cooper and Whitaker are veteran journalists, they have plenty of experience interviewing people, so chatting with the contestants should be easy for them.
"Who Wants to Be a Millionaire?" looks like it would actually be more stressful to host. You have to chat continuously with the contestant while they're thinking about the answer, and say meaningful things about the question and possible answers, but avoid revealing too much.
Trebek was also an executive producer of the show, and from reports and interviews I've heard he was very involved in the production. But I doubt guest hosts do much more than just host the episodes. Since each did two weeks of shows, and Jeopardy! tapes a week of shows in one day, it was just 2 days work for each of them.
I originally thought of posting this question when Cooper said it, but I thought he was just honoring Trebek's memory by saying something nice. But when Whitaker said the same thing, I decided it might not be just a pleasantry, maybe there's something to it. But what could that be?
Note that my question is specifically about guest hosting. As I pointed out above, Alex did much more work on the show than just hosting, but I don't expect that the guest hosts are as involved.