It just became not relevant ... Previously, many projects were successful due to the general confidence of investors
Now most of the then investors are skeptical of all projects.
It depends on the project maybe those you seen successful are the one who create a good marketing strategy and release more money just to make their project reliable, but we cannot deny the fact that even up till now we can see those fallen projects and statistically there's more failed than success since mose of the project right now are scams.
But I will not agree with OP that we shouldn't assume that the project we join will not successful since if that's the case I will not any of those since we are wasting our time and for sure the reason why people join in certain bounties since they believe that they will became successful and earn with them.
It is true that it is impossible that the reason I participated in the promotion of the project was the failure of the project, because many projects still survive and have a rewards and airdrop program. so the op reason doesn't make sense.