My Mazda 6 manual has a very smooth and light clutch and “hill assist” where the car will brake for you on hills as you ease into gear. It’s an awesome combo and I get virtually no fatigue from driving in stop and go traffic trough hilly areas. My old manual though was another story- you’d have a sore leg after a long drive in bad traffic, and getting stopped on a steep hill with the automatic drivers crawling right up to your rear was nerve wracking.

I do think the clutch is a factor. I've driven more "pure" sports cars and often their clutches require a lot of force. But I've never owned a car with a clutch like this. So yeah, maybe my comment was a bit naive.

For me, motorcycles in traffic has been painful due to having to hold a heavy clutch in with your hand.

Just an aside, you shouldn't be holding the clutch in much. Only when coming to a stop in first gear (hold until the vehicle behind you stops so you know you won't get rear ended) and when starting to move (i.e. a few seconds before a light changes, or once traffic clears and you're planning to start moving again). You should be in neutral while stopped otherwise.

If the clutch is a problem, it's time to change the master or the clutch cylinder or change the car.