The three pilgrim festivals were agricultural before they were anything else. Pesach falls at the barley harvest, Shavuot at the wheat harvest seven weeks later, and Sukkot at the ingathering of fruit at the end of the season, and each carries an offering appropriate to what has just been brought in. Centralising sacrifice in Jerusalem took that farming calendar and attached it to a single building, so that three times a year the population of a largely rural country was required to travel to one city and appear there.
E. P. Sanders's study of Jewish practice in the late Second Temple period works out what that meant in operation: the logistics of moving animals for sacrifice, the tithes that had to be brought or converted into money and spent in the city, the accommodation problem, and the priestly courses that rotated through service.
The commandment as stated in Deuteronomy applies to men and says that no one should appear empty handed, with the offering scaled to means. In practice whole households travelled, and the festivals were the occasions on which a dispersed people saw itself assembled. That experience, rather than the sacrifice itself, is what much of the later literature remembers about them.