Just finished my third Rick Steves tour, went to Barcelona and Madrid. Last year I went to Paris; pre-Covid I went to London. I think I know how to solve my problem, but wanted to put it out there.
I flew into Paris and Barcelona from the west coast of the U.S. and landed the day the tour started. I was incredibly tired, not just on the first day, but the 2nd and 3rd days, too. On the London tour I came a day earlier, it was much better regarding the lack of fatigue. The last two trips times were due to much cheaper flights landing on those Sundays.
Next year I want to do a Germany tour, would you recommend landing a day out or even more than that? I know coming the day of the tour isn't going to work anymore. I know I may have to pay more for the flight and of course a few nights of lodging, but it will probably be worth it.