Hi Daniel,
Thin content penalties are my least favorite because they are hard to recover from. I agree with Barry that all manual actions can be removed. However, from my experience it can be very difficult to recover traffic that's lost after a thin content penalty.
Please know I'm speaking in hypotheticals because every case is different and for some sites it takes a fair bit of digging in to really understand why Google gave this manual action.
Google only gives manual actions when their algorithms are not doing the job they want. It usually means that a site is having an unfair advantage because they're exploiting an SEO tactic, or sometimes several, that involves creating large amounts of content that only exist to try and capture search traffic.
It's certainly possible that having 3000 location pages is the culprit. However, I feel like Google's algorithms have evolved enough to take care of that kind of thing. Otherwise we would be seeing thin content penalties all over the place because lots of sites have doorway like content... content that really could just be one page or perhaps a small handful that has been made into thousands of pages for SEO reasons.
It also concerns me that you have spent hundreds of thousands on content. Now, There are many legitimate ways to spend money creating content that truly helps people. But if you got a thin content penalty it may be the Google has determined that all of your content is created just to rank on search engines as opposed to truly helping an audience. The manual action is a way of Google saying, "We don't want content from this site to rank but our algorithms are not doing a good enough job at suppressing it like we want."
It is difficult for content that is written by content writers to be considered high quality by Google these days. Here are Google's guidelines for creating high quality content:
https://developers.google.com/search/docs/fundamentals/creating-helpful-content
We don't see a lot of thin content penalties but today when we see them they're usually for really tricky manipulative things that site owners have been doing. Several sites that came to us with thin content penalties were running schemes where they had multiple sites all targeting the same thing. We could not get penalties lifted until we convinced Google that they would focus on just one site.
I'm happy to take a quick look if you want to reach out to me. I don't personally do manual actions anymore but if you need to hire someone to help you sort this out I can recommend someone whom I've trained.
There are some sites that fully recover from thin content penalties, so don't lose all hope. Personally, I feel we are about to see a huge shift in how people search on online as AI improves and gets more adopted. If I'm right, a lot of businesses that thrived on creating large amounts of content are about to go through some rocky times.
