Hi,
Although I am still fresh on Steemit, I also share your concerns.
However, I believe that you cannot lose what you don’t have at first place, with the exception of time lost in dead-end situations. As you said in your post, Facebook activity, for example, is not compensated through any monetary or other rewards, apart from the joy of social interaction, so Steemit activity is much better and rewarding in that sense, even if Steemit faces problems that can threaten its existence in future.
Personally, I have witnessed the rise and demise of websites that used to publish user-generated content and reward their writers, such as Infopirate, Helium.com, Triond.com, just to name a few. Some of these websites are no longer around, and some others have stopped offering their users any type of reward.
As long as there is quality and genuine interaction on Steemit, Steemit will continue to exist, although writers’ rewards may drop or rise. At least there will be some rewards.
One last thought is that, my experience with all these websites that I was part of made me wonder what really motivates me to write online. Because if I find a way to improve myself first, then it is possible to help others improve, as well. Just thinking that so many people are active on Facebook, without receiving any payment at all, makes you realize that people write and are active online, in order to express themselves, interact with other people, etc., with monetary (or cryptocurrency) rewards playing no role.
Of course, this does not mean that the content posted on Facebook or any other social media is necessarily of good quality. The key factor, I believe, is social approval.
Major newspapers keep publishing content that is written by professional journalists, and new books are being written every single day. However, even these articles and books are in need of curation, which is something that Steemit has already adopted.
Another point that I would like to make in this long comment, is that most online writers, including myself, fail to realize the importance of being focused on a specific niche or subject, rather than being a Jack of all trades. In this way, it will be easier to build and interact with a small community that shares the same interests more or less. I believe that this was the reason the social media were developed in the first place.