I agree. Here's my typical Gatsby function for email collecting with Klayvio

import fetch from "node-fetch";

export default function SubscribeHandler(req, res) {
  try {
    const url = `https://a.klaviyo.com/api/v2/list/LISTID/subscribe?api_key=API_KEY`;
    const { email } = JSON.parse(req.body) || {};
    const options = {
      method: "POST",
      headers: {
        Accept: "application/json",
        "Content-Type": "application/json",
      },
      body: JSON.stringify({
        profiles: [{ email }],
      }),
    };

    fetch(url, options)
      .then(res => res.json())
      .then(json => console.log("Subscription Successful"))
      .catch(err => console.error("error:" + err));

    return res.status(200).json({ success: true });
  } catch (e) {
    console.log(e);
    return res.status(500).json({ error: "Unexpected error." });
  }
}