Web development has stayed pretty democratic since the early days because there is a small number of people pushing technological boundaries while the vast majority work in a well understood space.
Game development has consistently been the opposite: in a race to better graphics, better physics, bigger and better everything, game complexity has only gone up. Companies are working with tech that is not open to access by "mere mortals" because they are often proprietary hardware from Microsoft/Sony/AMD/nVidia. As a result of the technological arms race, there is a LOT of platform fragmentation in the graphics world.
So the problem is that game development is consistently a "big team" task, and industry expertise is monopolized by companies. Tech trickles down very slowly to hobbyists, so while there are engines for the rest of us to use, they don't benefit from the kind of industry battle-testing that web technologies get.
Game engines like Unity and Godot seem to be changing this a little bit by simplifying game development - standardizing complexity by abstracting away low level optimization concerns that you'd really only care about when you need to push technological boundaries. But in general the concept of "convention over configuration" and its related ideas hasn't really caught on, so there isn't even a standard way of thinking about game engines.
The last thing to consider is how much more complex games are than web. Web is mostly a mixture of 2-D graphics and user input handling code. Games are often 3-D graphics (3-D is just much harder than 2-D), often have more algorithmically complex input problems, require audio, and sometimes require real-time networking for multiplayer (web can tolerate latency better). There's just a lot more in there.
Another problem: because of performance requirements, the vast majority of the core libraries for physics, graphics, etc. are written in C++. C++ is not easy to pick up.
Game development has consistently been the opposite: in a race to better graphics, better physics, bigger and better everything, game complexity has only gone up. Companies are working with tech that is not open to access by "mere mortals" because they are often proprietary hardware from Microsoft/Sony/AMD/nVidia. As a result of the technological arms race, there is a LOT of platform fragmentation in the graphics world.
So the problem is that game development is consistently a "big team" task, and industry expertise is monopolized by companies. Tech trickles down very slowly to hobbyists, so while there are engines for the rest of us to use, they don't benefit from the kind of industry battle-testing that web technologies get.
Game engines like Unity and Godot seem to be changing this a little bit by simplifying game development - standardizing complexity by abstracting away low level optimization concerns that you'd really only care about when you need to push technological boundaries. But in general the concept of "convention over configuration" and its related ideas hasn't really caught on, so there isn't even a standard way of thinking about game engines.
The last thing to consider is how much more complex games are than web. Web is mostly a mixture of 2-D graphics and user input handling code. Games are often 3-D graphics (3-D is just much harder than 2-D), often have more algorithmically complex input problems, require audio, and sometimes require real-time networking for multiplayer (web can tolerate latency better). There's just a lot more in there.
Another problem: because of performance requirements, the vast majority of the core libraries for physics, graphics, etc. are written in C++. C++ is not easy to pick up.