I didn’t participate in the clean-up effort so I’ll caveat this comment with: my feedback is as an observer.
Personally, I think reviving old threads is something that should be avoided and so while this makes sense as a one-off effort, future community work should focus on providing an answer when the thread is new. Providing meaningful support to other members of the community often requires dialogue and expertise, whereas a general no thread left behind initiative leads to threads that have a reply light on expertise (effectively, a reframing of the documentation) and without dialogue.
I think overall this effort has been a great success in addressing the backlog of unanswered threads, and certainly, there has been a great deal of valuable content created by the participants – especially @Simran-B! – but the effort itself is second-best to ensuring that threads have meaningful contributions when they’re created.
As a person asking questions on forums I greatly appreciate the time someone else takes to contribute to my threads but I find it frustrating when I receive a generic reply as it is a waste of my time and theirs. As a person answering questions, I choose to answer questions only where my experience and expertise can provide value, and I am ready to engage in a back-and-forth to take the question to a resolution.
With all that in mind, my suggestion going forward is to focus on connecting subject matter experts with relevant questions when they’re created. I don’t have a clear vision for how this could work in practice, but as a starting point, I think community “triage” of new threads is worth exploring: empower regular community members to defer to those with expertise. There are two forms I imagine this could take, either by finding an existing answer or by bringing in an expert to answer the question.
The triage process might be something like:
- Does an answer already exist to this question? 
- Do I know the answer to this question? 
- Do I know of someone on the forum who has expertise in this area that I can defer to?
For example, yesterday I responded to a question about Action concurrency because it’s an area I’ve been working a lot in recently and I happened across the thread. If I hadn’t seen the thread when I had the forum open, I wouldn’t have replied, and the question may have been left without a complete answer forever despite having many replies.
Anyway, they’re just some thoughts off the top of my head. I think this forum is pretty unique amongst product forums in that it doesn’t just question about which buttons to click, it’s questions that cover the entire project development lifecycle – from complex GitHub Action implementations to team strategy – and so there’s real value in connecting expertise with relevant threads.
 I think regular forum users often underestimate how valuable their knowledge of the forum is: the ability to search effectively requires a lot of context that a new user might not have, so a regular might be able to find an answer that a new user might not have been able to.
 Replying to a question is easy but often the easy answer is not a valuable answer, it’s important to find the balance between encouraging participation and discouraging answers for the sake of it.