How do you measure community-driven product launch success versus traditional launch metrics?
The short answer here is (unsatisfyingly): it depends.
I believe that a successful community-driven product launch is likely not marked by a traditional "pop" in metrics. If you really want a product to succeed long-term and drive growth in your community, it needs to develop over time so that it becomes a part of the community's fabric. I've seen products launch with a ton of fanfare, lots of marketing, and even a strong uptick in community engagement—only to fall off quickly because there was no true community-level fit for the product.
At Reddit, Community Product Marketing does inbound work that helps our product team build products that enhance our user and moderator experiences and outbound work that ensures our community understands the product's true value. It's a bit of a cliché, but it's true—oftentimes, the best marketing is not marketing. Instead, we want to see the community talking and advocating for our products amongst themselves and then watching for an upward trend in the key associated metrics over time that prove the product is successful.
While I recommend giving community-driven products time to find their footing, you do need to know when a product is not showing any signs of PMF, and it may be better to cut your losses and move on.