Many moons ago I had a discussion about something similar with Michael Son, right around the time when they had focused heavily on short comics, which hurt long form comics immensely (it's always something, isn't it).
He explained that they were seeing that long form comics (one of which yours is in a roundabout way), were dealing with a decrease in interaction the older the series got. I'm assuming this has to do with some of your old readers falling off (many of them may just not be into comics anymore).
Like I said, this was many years ago and many things have changed. Short comics aren't the big deal anymore, we now also have novels, premium etc. But I still do feel that some of the old sentiment holds true - How can older comics be kept alive and growing without having to rely on Tapas for advertisement?
Some of the more successful series give us a good hint, but I totally understand that not everyone wants to make a comic in specific genres just because they are doing well with audiences.
It really is a big conundrum. Let me know when you figure out the answer to this issue lol
Edit: A similar topic was discussed in below thread and Michael clarified that old sups don't hurt comics anymore. So my comment here isn't correct anmore. Take a look for the additional insight.