You are right on both the physical & metaphysical levels. As you said, heat is molecules vibrating. The frequency and intensity of the vibrations determine the color and brightness of the light given off. And that in turn is a function of the source materials.

Different heat sources will cook food differently. Microwaves mostly cook things by vibrating the water molecules inside them. Broilers and toasters mostly cook things by radiant heat, from the outside in. Conventional ovens rely on the non-radiant heat supplied after the elements have turned off, and cook slowly from the outside, but over time heating the insides enough to help cook themselves. Gas and electric ovens both work on that principle, and I suspect the food tastes the same for those. Wood-fired ovens flavor the food with wood smoke. Ditto camp fires.

To all these different cooking experiences, we all attach memories, and acquired tastes. So your feeling that crumpets toasted before a fire are nicer than crumpets toasted in a toaster is really your recognizing that the fire adds a different flavor than the electrical element, and you enjoy the ambiance of the fire, and the flavor, more than that of the toaster.

Food is also flavored by the company and the circumstances. Ask a Girl Guide about s'mores, for instance. :-)