Alcohol-free versions of familiar drinks rarely taste like thinner versions of the original. They taste different in specific ways, because ethanol was doing several jobs that end when it is removed.
Ethanol is the carrier for aroma
Most aroma compounds in a drink are more soluble in alcohol than in water, and ethanol evaporating from the surface carries them to the nose.
Remove the alcohol and those compounds stay in the liquid, so a drink can contain its full aromatic content and smell of almost nothing.
This is why de-alcoholised wine often reads as flat rather than fruity, even when analysis shows the aroma compounds are still present.
It contributes sweetness and weight
Ethanol tastes faintly sweet on its own and adds viscosity, giving a drink the body that distinguishes a spirit from flavoured water.
Producers compensate with sugars, glycerine or thickening agents, all of which restore some weight while changing the character.
Getting the balance right is difficult, since too little leaves the drink watery and too much makes it syrupy in a way alcohol never was.
The removal process costs something itself
Distilling alcohol out under vacuum keeps temperatures low but still strips volatile aromatics along with the ethanol.
Membrane filtration separates alcohol from the rest without heat, at the cost of a slower, more expensive process.
Some of the removed aroma can be captured and returned to the liquid afterwards, which is standard practice at the higher end and rarely at the lower.
Preservation becomes an active problem
Alcohol above a certain concentration prevents microbial growth, which is why spirits keep indefinitely without refrigeration.
An alcohol-free drink has no such protection and requires pasteurisation, sterile filtration, preservatives or cold storage.
Pasteurisation adds a cooked note of its own, which is another divergence from the original that has nothing to do with the missing alcohol.
The stronger products are built rather than stripped
Brewing a beer to a low alcohol level from the start, by limiting fermentable sugar or using a yeast that cannot ferment maltose, avoids the removal step entirely.
Alcohol-free spirits are increasingly designed as their own product, using distilled botanicals and bitter or pungent ingredients rather than imitating a specific spirit.
Those built products generally succeed more often than removal products, because they were never trying to survive the loss of an ingredient they had been designed around.