Senior tours

You might think you are speaking with the Rick Steves office staff...but most of the folks replying on the forums are part of the community as you now are. Occasionally a Rick Steves staff member will also reply and you will be able to tell who they are as they will have a RS logo beside their name.

I do agree with the city tours being perhaps more doable.

I also suggest you look at Road Scholar tours. This company used to be Elder Hostel but changed a number of years ago to Road Scholar. Their tours all have an activity level on them and they are pretty realistic to what you'll actually encounter. Some are very strenuous and some have less activity than others.

www.roadscholar.org

Where did you want to travel to?

Take a look at Rick Steves My Way Vacations, where you plan all daily sightseeing on your own and at your own pace. The only times you really need to "keep up" are on bus departure mornings. A couple of fully guided tours with less active ratings are the itineraries for Eastern France and for Scandinavia, but you should read through the day-by-day itinerary for any red flags specific to your situation.

A "My Way" tour might be a really good choice for sightseeing at your own pace. What you do need to consider are the elements you need to be able to handle on your own. Picking this up from one of the France tours:

"Our tours are physically active! It's an essential part of the Rick
Steves tour experience. On our My Way: France in 13 Days tour — among
other things — you'll need to happily… Carry/roll your luggage over
uneven pavement (possibly several blocks) and up stairways to reach
your hotel, then up several flights of stairs to reach your room.
Sleep with street noise and no (or weak) air conditioning. Be able to
navigate towns and cities on your own. Be responsible for your own
daily sightseeing, admissions, meals (except breakfasts), and
non-group transportation."

So if you are thinking you want a tour which offers more assistance and more creature comforts - such as good air conditioning and elevators - you might want to look at escorted tours that provide more help with luggage, public transit and whatnot, and different sorts of accommodations.

P.S. Not all "bus departure mornings" that I mentioned are strictly bus departures. On the Italy My Way tour, for instance, we'll walk with luggage (possibly over steps and bridges) to a vaporetto (public boat) stop in Venice and take that to the bus parking lot. Later in the Cinque Terre, we take a train with luggage, through stations that require carrying our bags up and down a flight of stairs. Et cetera.

City tours? David, I disagree, not all are suitable. Many are strenuous with much walking. No days of long bus rides to break it up. You are on the go all day every day. We took the London tour last summer. We loved it but several older seniors in our group had a lot of trouble keeping up. And if you need to stop and go back you are on your own navigating, not always easy if you are totally worn out.

You might look at Grand Circle or Viking River Cruises. (There are also some other companies.)
Most of the participants are older and the daily walking tours are pretty gentle.