Можно скрипт к такому виду привести

const platformButtons = document.querySelectorAll(".changer__platform");
const activeTargetClass = "platform__description_active";

platformButtons.forEach(tab => tab.addEventListener("click", () => {
    const target = document.querySelector(`#${tab.id}_desc`);
    const currentTarget = document.querySelector(`.${activeTargetClass}`);
    currentTarget && currentTarget.classList.remove(activeTargetClass);
    target && target.classList.add(activeTargetClass);
}));

Или короче для современных браузеров

const platformButtons = document.querySelectorAll(".changer__platform");
const activeTargetClass = "platform__description_active";

platformButtons.forEach(tab => tab.addEventListener("click", () => {
    document.querySelector(`.${activeTargetClass}`)?.classList.remove(activeTargetClass);
    document.querySelector(`#${tab.id}_desc`)?.classList.add(activeTargetClass);
}));