How They Do It
In the interest of scoring a breadth of wines, wine critics often taste wines en masse. Sometimes, this can mean up to 12 or 15 wines tasted at the winery with the producer. These tastings often yield great insight into the producer's philosophy, the whims of a vintage, and more.
But just as frequently, critics will taste wines in an organized tasting centered on a category of wines, usually in an even greater volume: such as 45 Chianti Classico Riserva from the 2019 vintage, or maybe 75-plus Châteauneuf-du-Pape from the same year. (This is also how competitions are conducted). Frequently, a publication's scores will be a mixture of these two types of scenarios. It should also be noted that the critic will be sipping and spitting 1- to 2-ounce pours for each wine to come up with their assessment. If they need more time with the wine, they may request another pour, but this varies from critic to critic.
Spitting is necessary to avoid intoxication, but it cannot avoid palate fatigue (i.e. the numbing of the palate's senses caused by the wine's acidity, tannin, alcohol, etc.). Professional critics are typically very good at managing their tastings in a way that provides a fair assessment for each wine, but every critic is philosophically and physiologically different on this front. Before you put any stock into a wine critic's scores, you owe it to yourself to become familiar with their process, as well as what they prize in a wine (it is much less universal than you might think).
Here is the rub: what you get from critics is an assessment of a wide variety of wines from a wide variety of categories. But these assessments are also conducted in a vacuum. In other words, a setting not at all similar to how you drink wine. While the wine is usually served at the right temperature and in the proper stemware, it is rarely given a few hours (or days) to evolve, and rarely served with a meal. Furthermore, as wine writer Andrew Jefford has pointed out, it is rarely even ingested, and digestibility could arguably be called the most important aspect of a wine. (Of course, there is no universal metric on such a thing given our widely ranging tolerances to wine).
The conclusion is this: a critical score can be valuable, but it must be seen in context — as a glimpse of a wine's potential. Wine critics would say much the same thing.