While I'll conceed that Great Britain does a much better job of adhering to your definition of "historic" than do we "yanks," I would counter by saying that what you see is all you're gonna get! The D&S runs passenger trains to and from Durango and Silverton. The run was called the "Silverton"! If you want to call it merely a tourist railroad then fine! What you see is what you get!
The C&TS purports to be more historic in how they operate their line. I would tend to agree but the object is to have a working passenger railroad! Trying to keep the railroad as authentic as possible is a worthy goal but there are degrees which make the British example totally unworkable!
First, the D&RG had the maroon cars and also the green ones. The D&RGW also had green and then changed to the gold ones. Most of the historic cars are on the D&S with the correct color scheme. So which color and name get's used to make the railroad "heritage historic"?
Second, the D&RGW was a Class #1 railroad and was eventually swallowed up by the Union Pacific which still owns the name and uses the colors and logo on it's own "heritage engines"! How could the C&TS and/or the D&S call themselves the D&RG (D&RGW?) when that entity is still legally a viable operation as part of the Union Pacific empire?
Third, the cost of running a steam operation is hideously expensive when one figures in maintenance, upkeep, restoration, INSURANCE, promotions, etc... While it would be nice to have an outdoor Smithsonian style museum exhibit where participants are able to experience the railroad as it truly was (does that include the horrendous railroad food that was the norm before Fred Harvey came along?) the facts say that such a venture would not be financially viable! This is where the C&TS is and what it is struggling with today.
Quite frankly, I find the whole notion of "my railroad is historic and yours is not" or "mine is MORE historic!" to be rather snobbishly arrogant. You are, of course, entitled to your opinion but the people that give their blood, sweat and tears to these operations deserve better. Too many have ceased operations. The ones we have left need to be treasured and preserved for our future generations. The people that are actively doing this deserve our gratitude and I'm getting the feeling that by criticizing whether a railroad is "historic" or not or is "more historic" is just doing them a disservice!
