I don't think so. They try as hard as possible. A lot of it is directly related to V8. In Node.JS v8.0.0 nightly they currently support 70% of the ES2015 spec without flags.
You can check the progress here: http://node.green/
You can check the progress here: http://node.green/
Node.js ES2015 Support is at 99% for v8.0.0 nightly.
Node.js ES2017 Support is at 74% for v8.0.0 nightly.