When I first visited Rothenburg in the 1970's, the go-to guide was the Michelin Green Guide. It only mentioned Miltenberg (no longer) and gave Rothenburg 3 stars. We visited both but liked Rothenburg much more. Rothenburg was not invented by Rick Steves.
Rothenburg has advantages: a well developed tourist industry, a mostly original wall and (for me) a wonderful setting perched above the Tauber River Valley. Walks down into the valley are as much to us on our visits as the towns sights. I also felt that Miltenberg had a beautiful setting.
As well as the famous "Blood Altar" in St. Jakobskirche by Riemenschneider, Rothenburg has a lesser know early work by him in the Franziskanerkirche picturing the Stigmata of St Francis. Down in the Tauber Valley in Detwang is the another Riemenschneider Altar in the St Peter St Paul church. As I really like Riemenschneider, these help draw me back.
Paul Schreckenbach wrote his historical novel, Der König von Rothenburg in 1910, which helped popularize the town. The book was just okay for me.
I understand there was an artist colony in Rothenburg in the early 1900's. I know that there are some interesting historical paintings of Rothenburg in the Reichsstadmuseum.
Rothenburg's fame as a tourist destination was started well before Rick Steves Books.
I have never visited Crime and Punishment (torture) museum or taken the Nightwatchman's Tour. Still I find much to do for 2 days in Rothenburg.
I hope to get back to Miltenburg. There are many places in Germany that I could say the same about.