Do you want to live in a world where everything can explained?

[Anomalocaris]

In this world, scientific discoveries and research have stopped: everything is known to mankind.

Back near the end of the 19th century, the bulk of physics community thought classical physics offered a comprehensive and accurate description of the universe, and that our understanding of the fundamental of how the universe works is essentially complete. All that remains is to apply this understanding diligently to describe observed phenomenon.

Essentially all insights have already been had, all it took was hard work to apply the insights.

In real life we know the adaquacy of classical physics was already in the process of proving to be wanting at the time. But it still does afford a good example of a closest practical approach to your world where basic knowledge of the universe is thought to be "complete".

Even so, even if no relativity or quantum mechanics was found to be necessary, you can see scientific discoveries and research will never stop. Sure we might know how in principle how gas behaves, but work out the detail of the eddies behind a bird's wing? That is still to be done. Work that out, there is another. Practical application of basic knowledge never stops and each would be a challenge in itself. Once the fundamental model of how things work is complete, research and discovery turns from fleshing out the fundamental model of how things work, to applying to model iteratively to describe and predict actual events with ever greater accuracy and precision.