Also, the intentionality of it being a designed world. Some implicit features are intentionally designed to be messages themselves.

For example, the point of there being close to no technological advance in thousand of years is intentional:

1. Saruman's plan consists on mass industrialization. Beginning in Isengard, but at the end of the books projected even further: globalized. And he is one of the villains!

2. During the millenia that technology hasn't advanced, the elves did rule. Other than the disaster caused by the villains of the story, Tolkien intentionally made the elves not need such technological advance. They had no incentives to, they had enough. Same with the rest of the races.

Those are two are messages Tolkien is telling to the reader. Shallowly described by me, of course.

I also understand this as the reason for the worldbuilding to be so limited and sparse. The world that we find is enough for his vision and messages to get across, and adding anything more would make it repetitive or distracting.