Babel throws a syntax error on arrow function

I'm trying to adapt this code for a small project with React, but I'm having trouble, and I don't know how to fix this, because I don't know if this is the original code or my Babel that's buggy (like, missing a library or something), or if I can't because React.

So the thing is I had to adapt some functions because otherwise Babel would throw an unexpected token on them, i.e,

static propTypes = { // unexpected '='
  onRequestSort: PropTypes.func.isRequired,
  onSelectAllClick: PropTypes.func.isRequired,
  order: PropTypes.string.isRequired,
  orderBy: PropTypes.string.isRequired,
};

became

static get propTypes() {
    return {
        onRequestSort: PropTypes.func.isRequired,
        onSelectAllClick: PropTypes.func.isRequired,
        order: PropTypes.string.isRequired,
        orderBy: PropTypes.string.isRequired,
    }
}

and this:

handleRequestSort = (event, property) => { ... } // unexpected '='

became this:

handleRequestSort(event, property) { ... }

For my main issue, I replaced this:

createSortHandler = property => event => { // unexpected '='
    this.props.onRequestSort(event, property);
};

by this

createSortHandler(property) {
    return function (event) {
        this.props.onRequestSort(event, property);
    };
};

However, if I click on the arrow on the table that triggers the order's change, I get cannot read props of undefined. Otherwise, I get `unexpected token '=', as written in my code.

So my question is the following: is the original code buggy, is it my babel or is it something else? I'm currently on a Rails base with webpacker, but i don't believe this is the reason why I have these issues.