Turing completeness isn't about having everything you need to build the physical computer, just about expressing program logic that can perform a certain class of unbounded computations. Like, given any C program's logic that takes some input and gives an output, you could calculate the same thing (painfully) with NAND gates.

Anyway, bringing up Turing completeness is overly theoretical when talking about a programming language. It's pretty hard to make a language not Turing-complete, and it doesn't say much about what you can use it for IRL.

> you need to build the physical computer

Exactly.

Now tell me how you will do unbound computation (ie. write on the n+1 cell in the Turing machine) with a fixed number og NAND gates and without a clock.

Oh, I see what you mean. Yeah it seems like you need a clock.