Don't use isLoading booleans as source of truth.

Why? to avoid impossible states. If an error happens when fetching users, we would have an impossible state for a fraction of ms:

const App = () => {
  const [isLoading, setIsLoading] = React.useState(false);
  const [error, setError] = React.useState("");

  const fetchUsers = async () => {
    try {
      setIsLoading(true);
      fetch(/*... */);
    } catch (error) {
      setError("Upps, an error occurred");
    } finally {
      setIsLoading(false);
    }
  };

  React.useEffect(() => {
    fetchUsers();
  }, []);

  if (isLoading) {
    return <p>Is Loading ... </p>;
  }

  if (error) {
    return <p>{error} </p>;
  }

  return <p>Great we have some users data</p>;
};

Use boolean variables that are derived from a source of truth:

Our source of truth is status. We can create boolean variables derived from that like so:

const App = () => {
  const [status, setStatus] = React.useState("idle");

  const fetchUsers = async () => {
    try {
      setStatus("pending");
      fetch(/*...*/);
      setStatus("successful");
    } catch (error) {
      setStatus("rejected");
    }
  };

  React.useEffect(() => {
    fetchUsers();
  }, []);

  if (status === "pending" || status === "idle") {
    return <p>Is Loading... </p>;
  }
  if ((status = "rejected")) {
    return <p>Upps, an error occurred </p>;
  }

  return <p>Great we have some users data</p>;
};