You're comparing totally different tech, a jet and a conventional plane. In trek terms, that'd be like comparing a warp driven starship with a garbage scow. The TOS ship and the TNG ship have similar function and capability, so you need to find a different analogy (like how different a Cessna is from a spad or fokker ... is it all that different?)
The starships being discussed have warp drive nacelles, saucers, engineering hulls and various features like impulse engines and deflectors. The aircreaft I compared have an airfoils (wings), tailplanes, elevators, cockpits, and method of propulsion. If you object to the engine types, let's do prop to prop, jet to jet, fighter to fighter, airliner to airliner. A Spad and a P38. An F-80 and a F-117. A 707 and a Concorde. A YB-49 and an XB-70, or a B-47 and a B-1.
As different in lines and forms as the TOS ship and the D. Shall I continue hauling out examples?