What would have made Enterprise a "legimate" prequel?
I dunno...perhaps making something like how Spock descibed the era in "Balance of Terror?"
SPOCK: As you may recall from your histories, this conflict was fought, by our standards today, with primitive atomic weapons and in primitive space vessels which allowed no quarter, no captives. Nor was there even ship-to-ship visual communication. Therefore, no human, Romulan, or ally has ever seen the other.
Constantly referring to concepts from newer shows can be immersion breaking, I get that.
Though I suppose for me such annoyance would be more in the direction of 'phase pistols' instead of 'phasers', 'photonic torpedoes' instead of 'photon torpedoes', 'polarize the hull plating' instead of 'raise shields', etc. ...
That was ENT's problem: There was little to no worldbuilding. They just took concepts that already existed and slightly tweaked their names. And honestly, how could they worldbuild when the show started immediately after VOY ended?