Is there something that really helped after getting hit by the big G?

I am currently trying to "save" a website which got hit by the Google Updates. Plus I am doing a kind of case study and am writing about everything I have done so far.

Is there anything that worked for you?

Let me know so I can try it out.

So far this did not work:

1. E-E-A-T signals did not change a thing
2. Changing Plugins / SEO-Plugins (did not think it would but why not try at this point)
3. Backlinks did not help. Yes, they were high quality, yadayadayada
4. Social Profiles and Social Media didn´t help
5. Disavowing Links did not bring shit
6. "Forbidden" Keywords like "best" or "buying": Deleting all old content (which was not ranking anyway anymore) only resulted in a drop in Domain Rank, redirected it via 301 so should be fine
7. Duplicate / Thin Content through categories or tags: Deindexing or Indexing doesn´t do anything

Ideas that need to be tested:

1. Adding a Forum could be helping
2. Noindexing/deleting old content without traffic

Any ideas

Google will hit you in 2 ways.
1) you traffic goes down to almost 0
2) you loose a percent of traffic like 25% 30% etc

In 1st case just migrate the content to a different domain and delete the old website, deindex the domain, do not do 301 redirect.

In 2nd case do what you can to improve you site. Then publish new post for a few keywords low competition and allintitle<10.
If you are able to rank a few keywords then continue with the site.
If non of the keywords ranked then do the same as 1st case.