Sure I can understand that if you backed the Kickstarter and haven't gotten all of your rewards yet. He's definitely taking a long time on some of those rewards (for my part, I think I've gotten everything I signed on for), but unless you're a Patreon backer and he's not coming through with his promised output, it's hard to see what the complaint is. I've bought books and other merchandise too, but don't think I'm owed anything beyond the specific stuff I paid for.
He bit off way more than he could chew with the Kickstarter, and he's said as much. The fact that he's still working down that backlog, years later--rather than throwing up his hands and saying "Sorry, can't do it"--is pretty impressive. Particularly when you add in his health problems.