There's a large company (30000~ employees, market cap "north of $3 billion") called Rocket Internet [0], based mostly (solely?) on the business strategy of building something that already exists.
Seeing how successful they are, it seems the "uniqueness of a product/service idea" is not such an important factor as it's commonly considered. Perhaps it's more about the execution, how the idea is implemented - UX, marketing, etc.
Worth mentioning that they only work in a very specific niche — e-commerce sites. That's literally the only thing they do, although admittedly very well.
Seeing how successful they are, it seems the "uniqueness of a product/service idea" is not such an important factor as it's commonly considered. Perhaps it's more about the execution, how the idea is implemented - UX, marketing, etc.
[0] https://thehustle.co/rocket-internet-oliver-samwer