Death Valley is quite heavily visited in the summer months now, which is in contrast to the 1950s and 1960s -- when few cars had air conditioning. European tourists find it interesting and compelling, especially considering the extremes in temperature and elevation in a desert environment. There's nothing wrong with this, as long as due caution and care is taken.

The original itinerary included too much. The revised itinerary looks much more reasonable. There's a difference between driving to all of these places and enjoying what the places have to offer. It is likely possible to phyiscally make the original itinerary, but it would hardly be an enjoyable trip.