Star Trek The Motion Picture (or The Motion Sickness, as I've heard it called) isn't much as an entertainment (all right, so you get to catch Persis Khambatta's breasts wobbling) but it's an excellent metaphor for a basic problem that the Trek cosmos is always trying to get around. The Sixties Trek was an obviously cheap show. Then, years later, after Star Wars and Close Encounters, it started coming back. the comeback began with Star Trek the Motion Picture, about a vast alien entity called V'ger heading for Earth. Turns out that at the core of this vast complex entity, however, is a stunningly aniclimactic machine, an old Voyager probe that superadvanced aliens decided to enhance for the hell of it. As the Voyager probe is distinctly overshadowed by all the additions, so Star Trek The Original Series stands overshadowed by the procuction values of all that has come after it. It's an extremely uneasy fit, just like the probe within the grand "V'ger" clous -- but fit it must. It's an unenviable task. Bottom line: if Klingons could have had as much makeup in the Sixties as they did later, they would have.
Personally, I miss the ST:TOS Klingons -- not just in appearance, but attitude. They were basically Stalinists of the Stars. Then they got reinvented into professional wrestlers. Entertaining, sure, but something to build a whole civilization on? After a while of getting to know Klingons and Vulcans and Ferengi, I begin to miss the good old days of Jonathan Swift, when he could set metaphorical parallel humanities on a single island.