We're not unicellular organisms, though.

Also the wiki page also states that 90% of the metabolism happens in the liver

That's true of quite a few macronutrients we eat.

Fructose needs to be metabolized in the liver, which converts some of it into glucose or lactate, which then circulates to cells that will use either in respiration. It also gets converted to glycogen stored in the liver, which can then be used to converted into glucose as needed for regulating blood glucose.

Lipid metabolism, which also relies on the liver, has fatty acids assembled into triglycerides, and circulated to where cells can take them in as free fatty acids and glycerol, for cellular respiration through beta oxidation.

Starches and other complex carbohydrates are split up by enzymes in saliva or fermented in the gut, often by microbes, releasing glucose that can enter the bloodstream.

Alcohol metabolism results in acetate both in the liver and circulating in the body. The acetate is metabolized into acetyl-CoA, which is used for synthesizing fatty acids (which can be used for cellular respiration or converted to triglycerides for longer term storage). Acetate can also directly support cellular respiration in the brain, as an alternative to glucose, and chronic alcoholics often have brain tissue that has adapted to use more acetate than glucose.

The point, though, is that all the different metabolic pathways result in oxygen being consumed and carbon dioxide being produced. The limited abilities of specific cells to make use of certain compounds doesn't change the fact that the entire body has organs that help process what we eat into what our cells can use.