I have no particular axe to grind with regard to wine scores. Consumers seem to like them because they are convenient. However, there is no doubt they over-simplify the complex topic of wine quality and give a misleading picture if used without the accompanying tasting notes.
There is however one argument against wine scores that doesn’t work. People often point to the absurdity of assigning a score to Beethoven’s 9th Symphony or Picasso’s Guernica and then argue that wine scores are absurd for similar reasons. But the cases are not at all analogous.
The difference is that the works of Beethoven and Picasso are already part of the art canon. Their iconic status was decided over a century ago and there is no serious challenge to it. Scoring their work would perform no useful function even if we could decide on what criteria to use.
In essence the work of great composers and painters from the past are no longer in a market that the public has access to. There is a market for performances of Beethoven but not the work itself. And the market for paintings by the great masters is among museums and wealthy private patrons, neither of which need scores to direct their purchases.
Notice that film and contemporary popular music do receive scores on sites like Metacritic and Rotten Tomatoes. This is because, like wine, there is a publicly accessible market for them.
Furthermore, unlike paintings and the score of musical works, wines change from year to year. Vintage variation requires we have a means of tracking those changes. Wine scores are one convenient way of doing so.
They may be arbitrary or simple-minded but wine scores do satisfy a need and have a clear function.