So Pat - There are two things that you could do here
1) Your isolate layer function works to show the data on a layer - CTRL A to select All and have the properties Pane open - if the data selected is all lines - the Name field should be either empty (if all lines are unnamed) or Varies (if some do and some do not have names. You can select the name field in properties Pane and change it for all selected data items. If you are pcking non line objects (objects that have different element types, you can use the CAD View Filter (Turn it on in advanced View Filters) and turn off the CAD Object types you dont want to select (Text, Blocks etc) and then when you do CTRL A you will only select Line Items. This agreed takes a while, - if before you start the Isolate Layer you have all the linework that you want to name visible, you may also want to Hide Layers that are switched off (in VFM you can do that to reduce the list of layers to just the layers that are visible - that would also make it faster (agree still a macro command to do this would be an improvement and fastest approach
2) To get the Layers that you have you have likely used Standardized Layers to take imported data on CAD Layers that have poor names - and place the objects on Layers with names that you want to have. In this process, Standardize Layers can rename the objects as well as it moves them to new layers and it names them with the name of the target layers. I do this all the time and it works pretty well because i want eveything named and layered before I start doing Data prep or Takeoff work.
I still agree that a command to rename on mass would be great and useful and likely not a tonne of work
Alan