Since water changes place stress on fish and ecosystem, by altering the tank's self-imposed balance of micro-organism density, reducing the amount of nutrients, et cetera, water changes were never anything better than a necessary evil.
see, this statement from the OP shows their lack of knowledge. seriously.
water changes do not alter the "self imposed balance of micro organism density".
doing a water change removes very little beneficial bacterial. hardly any. its neglegable.
secondly, doing a water change can correct the problem of excess wastes in the tank, and can restore a tank to healthy water conditions by creating removing and diluting wates (such as ammonia and nitrite) such that the existing bacterial population can handle the post water change levels, but could not process the pre-water change levels.
when you do a water change on a tank with high ammonia, you have a situation where you have bacteria in the tank but not enough to oxidize the current ammonia levels. post water change, the same population can then handle the ammonia (and reduce the previously high ammonia reading to zero)
we are debating with someone who does not understand what they are trying to debate about.
its that simple.