Pretty sure Thunderlord quest is available to everyone who has Destiny 2, just like last time, so it's not paid content in the way you mean. Secondly, I think you're being quite unfair referring to casuals who couldn't be bothered to finish it last time, as it was a timed quest over the Christmas Holidays. Thousands of players were probably doing family Christmas stuff instead of playing Destiny every day. And before you start, I wasn't one of them. I have no life and got it on all 3 characters.