I run engineering at Operation Code https://operationcode.org/ https://github.com/operationcode/
We've been massive fans of Hacktoberfest for the last 3 years because it has brought a MINIMUM 300% increase in quality pull requests compared to even the next best month of the year.
I even put my own money on the line to double down on the incentives with extra prizes in exchange for resolving multiple issues. I've made friends and long-term coding partners from the event as well.
I hope they never end Hacktoberfest, but I think they should definitely offer the ability for you to signal/flag that you're not interested in participating as a repository.