JS does not need to be over complicated

poem.js

/**
 * @typedef {object} PoemData
 * @prop {string} title
 * @prop {string} author
 * @prop {string[]} lines
 * @prop {string} linecount
 */

const container = document.getElementById('poem-cont');

container.innerHTML = 'Loading poem…';

const response = await fetch('https://poems.4-walls.net/random');

if (!response.ok) {
  throw new Error(
    `Unable to fetch poem data: ${response.statusText}`,
    { cause: response },
  );
}

/** @type {PoemData[]} */
const [poemData] = await response.json();

container.innerHTML = `<h2></h2><cite></cite><p></p>`;
container.querySelector('h2').textContent = poemData.title;
container.querySelector('cite').textContent = poemData.author;

const poemContainer = cont.querySelector('p');

for (const line of poemData.lines) {
  poemContainer.append(line, document.createElement('br'));
}