They were able to release more updates in the past. What changed? The standard you people are talking about was different, much shorter before. And we see again and again many devs who were able to release numerous updates per year went to single update per year, if not longer. So what changed? I tell you, fat wallets do not contribute to faster development process. Why bother if you have stable income per month. Yes, real life stuff can be a reason as well, but not always, and we are talking about a widespread issue right now.
A lot changed depending on the game.
1. Quality of image definitely changed from 5 years ago when it was common to have 4-6 week cycle per update. Rendering time definitely increased quite significantly.
2. Writing time changed. Early on, it's easy to write something as an idea. It's much harder to write the continuation, especially if considering player feedback. You need to remember the vast majority of these devs are amateurs who never wrote anything before.
3. Quality of writing changed. Porn game market is extremely saturated now, much more than 5 years ago. There is tendency that devs felt the need that their writing need to be high quality to stand out in the market. This takes time.
4. Player demand changed. In general, "longer update for more content" is often preferable than "quicker update for less content".
5. Time is money, and both are limited. I'll use this game as an example. Patreon page around $600/month. The dev take home less than that because Patreon took a cut. Depending on where you live, that's nowhere near liveable wage. You can't expect this to be a full time job. Devs might be willing to take a chance early on in hope that their game caught big support, but they can't do that forever. There needs to be a time where they have to make a decision on whether to go full-time on the game, part-time on the game, or abandon the game.
6. More money can easily lead to ill-advised bigger dream. There are games that make a lot of money and that led to the devs getting more and more grand vision of their game because they think they have the monetary support to do that. Have a look at Star Citizen that has almost 900 MILLION crowdfunding and still nowhere near close to full release because they probably don't realize their fantasy might never be realized.
To oversimplify and say that devs just want to coast is extremely silly. There are definitely devs that milk their games, but milking should only be used to those that the game is either "dead" (devs have no desire to continue/complete the game), or making A LOT of money but with extremely slow prolonged development time that isn't comparable to the monetary support.
IMO, the "blame" is often at the patrons' hands for enabling such behavior. That's why I always check before supporting a dev. If they are already making a lot of money, I don't care how good the game is, I'm not supporting them because they already have way more than enough. Instead, I will support those that are small-medium sized to keep their game going. However, ultimately, it's someone else's money and they are free to do whatever they want with it. If they want to spend $50/month ($600/year) on a game that gives one update a year, who am I to say they cannot pay $600 for an update?
Lastly, there are still games that release updates every 4-6 weeks. They are just aiming for different market than the ones taking longer.