You are absolutely right. The number of VNs I really enjoy playing is 7-8, and these are people who have been developing games for at least 2-3 years, and most of them release an update once a year. In the last year or two, successful developers who started new and stayed in the business have become very rare. I think the golden years 2018-2022 will see a collapse after that.
Developing these AVNs is hard. Speaking as a failed developer, I can tell you it's not easy. You spend hours working on just a handful of images. Getting the lighting in place, tweaking the models, getting assets like clothing to fit right, writing, coding, testing... If you want to produce a couple hundred images a month as well as the dialogue, coding etc, you would have to work at least 20-30 hrs a week to get it done well. Most devs are only good at one or two of these things which is why you can have a beautiful game with horrible dialogue or visa versa. In my case, I tried the month at a time release and ended up producing mediocre crap I was not happy with and I was working my ass off. Full time job and then developing.
Plus, you have to be dedicated, organised and focused to produce one of these things, especially alone. I have no clue how someone like Pink Cake does it. Even if you don't like BaDIK, you have to respect the work ethic. Creating new mini games, free roams, keeping track of all the paths and choice impacts, it's amazing some of the subtle differences in dialogue there are in paths. As far as I know, it's just one person doing all of this. It blows my mind.
Anyway, this is one reason why you see some really great launches and a solid release or two before the reality of what they signed up for actually hits and they bail. Sure, sometimes a young dev with a solid start can see a bunch of money rolling in and then lose their way as they suddenly feel they have to answer to all these people who give them money instead of just focusing on their work. I am sure there are people too who start something to generate some cash and then milk their donors, but I would like to think most devs are not like that. They just bit off more then they could handle.
Anyway, my TL;DR is, while the volume of new releases may not be as high as 18-22, the quality has gotten way better. There have been some really great releases with some really great productions and yes, they are taking longer than a month or so to produce a release so but it is worth it in a lot of cases.