From my experience you're wrong - the average TP today has, if anything, better people skills than yesteryear. Flight test nowadays is so complex - large chunks don't even happen on the aircraft - that pilots, engineers, mechanics and all the FT personnel down to the lowliest clerk have to work together to accomplish the task safely & economically.
As Self Loading Ballast on a program that used pilots from all over North America & Europe, I came to have a fine appreciation for the Pre-flight briefing. The better the brief (think CRM) the easier & more productive the flight.