Alright, I'll bite.

This is my `sf::base::Optional<T>` template class, a lightweight replacement for `std::optional` with same semantics: https://github.com/vittorioromeo/VRSFML/blob/master/include/...

This is what ClangBuildAnalyzer reports:

  **** Template sets that took longest to instantiate:
     833 ms: sf::base::Optional<$> (911 times, avg 0 ms)

Each individual instantiation of this class is sub 1ms. Including the header itself takes 3ms.

I'm sure I can optimize it even further if I wanted to.

---

Now to refute your other incorrect claims:

> The point of templates is generic programming, reusable components.

That's ONE use case. A more general use case is just reducing code repetition in a type-safe manner, which is extremely useful even within the same translation unit. Another use case is metaprogramming. And I'm sure I can come up with more. Templates are a versatile tool.

> And if you have to "selectively pick TUs where they're instantiated", you're basically admitting that you have to invest effort to reduce compile times.

...well, yeah? Of course you have to put in effort to reduce compile times. That doesn't undermine my point at all.

C++ templates are not slow to compile.