They did not go out of business, but service is not available to US residents as well as a few other countries. Their Mastercard is only available to SEPA countries too.
The rest of us can only move money in or out of Neteller via another visa card, Bank or Cryptocurrency. Bank account is normally the easiest method it is relatively cheap and fast compared to other similar ewallets. Costing for a withdrawal transfer about $10 USD and takes about 3-5 working days.
You can use Neteller to withdraw and deposit with almost every Poker Site and best of all there are no fees to do so.
Their sister site Skrill is the same as well. I call them the sister site because the same company owns and operates them both and they are essentially the same service. I use Skrill mostly these days though.