@Autumn thanks for the question! Sticky tent/rainfly material is fairly common over time and unfortunately doesn't have a surefire solution. Here's an article from Outside magazine with some tips on how to try to "fix" a sticky rainfly - we see mixed results in removing the stickiness and often the success of any treatment will likely depend on the severity of the stickiness and the age of the tent/rainfly.
I have an older quarter dome as well, and experienced the same thing. I was able to lay it out in the sun which fixed most of this, I think I may have sprayed it with a garden hose in the backyard.
After which I sprayed it down with a can of waterproofing from walmart. I took it out of storage for a backpacking trip to iceland last summer (2019).
the tent is heavier than my others, but extremely durable, so it got the 'nod' to travel.
here's some pix of it in action.