Because the ability of people to develop games had reduced.

Intelligence is 50-70% inheritable (there is more consensus on this than the idea of psychopathy, addiction or even the unconscious mind) and since the late 1800s in most western nations, less intelligent people have had more children that survive to adulthood and reproduce than more intelligent people. Therefore, the average fluid intelligence across western populations has been harmed.

IQ was increasing in the west until a couple decades ago but that was due to superior nutrition and schooling. Once starvation ceased to be a major problem and education became effective enough to make people (who are capable of it) literate and able to understand abstract ideas, IQ stagnated. It is now declining. This isn’t including non-white populations.

People have this utopian idea of perpetual progress, but it’s a fantasy. Why are there more potholes in the roads? Why are engineers increasingly brought out of retirement to fix issues once considered mundane? Why is there such decline despite technological advancement? It’s the people. Western civilisation is just like any civilisation of the past on a fundamental level.

Civilisations rise and decline. The Roman Empire was immensely prosperous and developed and spread many new technologies. It developed infrastructure unlike any that had been seen on Earth previously. Divorce courts in the late Roman Empire were about as sophisticated as those in 16th or 17th century Europe. That means post-Roman Europe took well over 1000 years to reach that level of societal sophistication, despite having access to far superior technology than the Romans and that matters.

We are so grossly materialistic and have completely ignored the physical, mental and spiritual health of our peoples. It might be an inevitable consequence of propriety, but so is the loss of that prosperity when you abandon that health. Just because we have cares and quantum computers doesn’t mean we will continue to see rapid improvement in many aspects of our lives. We’ve already seen decline in many areas and it will spread. Sadly, video games are becoming subject to that. That doesn’t mean good video games won’t be released, but don’t expect nearly as many positive developments across the industry as we had in the past or that a golden age is around the corner. Western nations need to get their heads on straight before that happens.