Show people this image when they worry about building something that has already been built

My point was to say that we don't need to build something unique.

A very good metaphor that @csallen once said (I think it was him): Why are there so many Italian restaurants, sometimes more than one in the same street?

Because people want to eat Italian food. The demand is already there. Restaurant owners are not afraid of opening a new Italian restaurant just because there are others already.

Another good example is @asmartbear and @mijustin said about the ice cream stand:

If you set up an ice cream stand on a busy beach, on a hot day, you'll easily attract a crowd.
Even if it means staying side-by-side with an existing one.

Building something similar to something already existing is inevitable...

But fear not.
Differentiation is key - in all market conditions

IMO if you're able to clearly answer the 2 golden questions

1. "is my idea solving a real problem, for which someone would be willing to pay ?"
2. "what the heck is it that makes my idea unique and standing apart ?"

then you're set to succeed

Then you just need to make your idea known - and that's where marketing comes in.

...In your case here, just wrap your "unicorn water" bottles in non-blu/cyan plastics and be noticed! :)

That is an example of commoditized market. In this case customer will choose just a cheaper version. To stand out you need to have a unique selling point. Without USP it would be harder to sell your product

Hehe, good one! 😁

there is a thing which was prefectly described in Zero-to-One book by Peter Tiel.

Every firm in a competitive market is undifferentiated and sells the same homogeneous products.

If all products are the same, it's "Perfect competition" and it destroy profits.