I am literally a programmer as my day job. Knowing how to make a game is easy. the time it takes takes effort. Physical labor isn't the definition of effort. Mental labor takes a bigger toll. Especially when someone has a day job. The dev is clearly trying a lot.
i may be wrong, but it seems to me that you joined late to the party and now you kind of misjudge the situation. The root of people's complaints here is not game development itself with it's difficulties and challenges. The problem is that Abelius could be a good developer, but 2 very consistent faults stop him and this game from success.
The main problem is the dev's ego, plain and simple. He is grateful and gracious when it comes to accepting praise and donations, but he ignores suggestions and blocks or bans criticism. The other is his predictably misleading communication.
To not be a hater, here are some examples:
Ignoring suggestions on it's own is not a fault but as everything else it can be taken too far. A short while ago he ran a poll among his subscribes to ask whether they wanted new locations or to develop existing ones further. Since erotic progression basically starts over for each location, people voted for the development of existing ones.
But that's not what Abelius wanted so he promised that more than half of the new updates will be focused on existing locations, with the caveat that any freshly created area will be counted as "existing location" by the patch after their release. This gives him free reign to ignore the wish of his highest paying supporters that he directly asked for.
Even more recently he fired the artist that drew everything in this game. When pressed for an explanation he said that since he (Abelius) does everything alone he wanted to cut the artist's salary to match their percentage of work done. But Abelius is the boss, so he basically didn't give his employee anything to do and then used this to justify a pay cut. But he reassured his supporters that this game won't need new artwork for years.
His contempt for his community was shown a few years back when he set the hard cap of the in game stats. The conflict was caused by people who simply went into the files and edited the numbers to unlock clothes that are still unavailable to the best of my knowledge. The dev responded by creating a system that hard resets the stats regularly to make file editing useless.
Overall his popularity stared to fade when he went on long rants about how he deserves more money than the 8-9k / month he got, because of all the work he did alone. He then schemed for months to "free himself from the shackles" of the people who paid him said 8-9k. He wanted to find a way to get that money without the people having a chance to voice their opinion.
So when you see people flaming at the development of his game, just know that it didn't start out that way. For the first 2 years this community was extremely supportive and defensive, but they have been burned way to much to keep that up.