RuPaul will demonstrate how I feel when people claim molecular mixology has nothing molecular going on with it.
It's all about taste. Form
in mixology should follow the function of alcohol as a social lubricant
in the most tasteful manner possible. If you want to get drunk, go to a
dive and get your Four Hors
Many molecular 'mixology' drinks have sugars and alcohol as the flavor base, or various permutations of simple syrup (Grenadine, Rose's Lime, fruit juices and syrups). You're not flavoring a protein like Fish or Poultry, where there are far more complex things going on at higher, sustained temperatures. As a result, my aim at the bar is to give new form and texture to familiar drink flavors. With this aim, giving something "new form" does not always require nerding out on molecular reactions. Sometimes, it's just about adding air.
There are molecular reactions. Alcohol has an effect on proteins, fat, temperature, mouth-feel, you name it. Depending on which liqueur used to make foam (in something like my Irish Russian Coffee), I decide on protein to stabilize that foam: soy protein, egg, maybe something algae based. Alcohol also monkeys with how that foam interacts with other seemingly unimportant elements of the drink -- the garnish, the color, the clarity of a drink, the rate at which the ice cubes melt. All of these nuances are directly related to the molecular properties of your ingredients and how they interact with one another.
For example, high-alcohol liquors (like 151) aren't the best to use in anything with heavy cream. The alcohol breaks down some of the fat in the cream, and.... simply isn't tasty. 151 is notorious in my cream experiments for leaving weird beads of fat or oil on top of the drink. It just tastes bad to me. I tend to avoid it, despite its awesome combustion abilities.
Other bar items that do explicitly have a molecular bent to them are faux caviars, cider-spiced mousse, and certain absinthe creations. There are huge reactions among the chemicals in them, that I think, are far more pronounced than in 'regular' molecular gastronomy recipes and cuisine. Some change the base flavor.
What I do is at the bar. The vast majority of the items I make are prepared cold, and I have no burners behind a bar. I work in very low fixed temperatures as a result.
Also, there is a disincentive for some intense molecular reactions. When you deal with alcohol, especially high-proof alcohols, the combination of alcohol and whatever other ingredients you're working with might not only taste bad, but creates an environment for really toxic by-products if you don't know what you're doing. Kinda like how sous-vide leaves the possibility wide open for botulism to develop in your meat.