This is quite an interesting case study. You see, by default, Google ignores bad links and negative SEO attacks are factored into the algorithms in order to protect a site. More than often post 2020, Google will now actually award a site that has had a negative SEO attack in response to the attacker.
You see, due to the fact Google now automatically ignores bad links the only time you should ever use the disavow tool is when you receive a "Manual Penalty" or you have overoptimized anchor text. (using the same keyword too many times)
If you check Google search console and you don't see a manual penalty, then your rankings loss has nothing to do with Google slamming you due to this so-called negative SEO attack. It won't even be an algorithmic penalty.
The other thing to note here, the disavowl links tool does not work right away. Your disavowl file can take up to 45 days to get crawled. Each time you update or resubmit to the disavowl tool this 45 days gets reset. So only submit once every 45 days.
As Google is currently making many ongoing changes, especially since the October spam updates, I would be checking a few other things before settling that this was due to the negative SEO attack. You could have a new onpage SEO issue.
For instance, (just an example) if your homepage has more than 3 H1 tags, your rankings can tank or even get deindexd altogether. Is your rankings still holding okay in Bing?
No, don't start a new domain and site just yet. If you don't have on page SEO knowledge, hire someone who does to check out some of the technical stuff first, also, wait at least 30 days for the disavow to work and check search console for errors or issues.
Additionally, only use the disavow tool if you are a gun on this subject, more than too often people use the tool incorrectly and can disavow links that are actually giving you some positive SERP impact.
Feel free to send me a personal message, happy to check out the domain and provide some free advice.
