There are use cases for which reflection is very useful. Things like automatic serialization are an obvious example. There's also automatic printing of complex types, automatic guis (think unity).

There are a few use cases which aren't very obvious like having a vector for each element in a structure instead of having a vector of the structure. This greatly improves cache locality and can be a great gain in performance for some applications.

Of course this is more introspection which is a specific case of reflection but all these examples are definitely not 'ugly hacks' and could greatly improve C++ as a language.

Then why do the solutions people use to work around the absence of reflection always seem to suck so much? They're (in some combination) verbose, highly un-DRY, require spectacular feats of type-system-fu, and at the end of the day they deliver capabilities that come up laughably short of their competition in other languages. I'm still waiting for a member of the "Reflection is Useless" crowd to show me a serialization framework on par with what I find in Java (100% DRY, 100% automatic for POD, 100% override-able without a type repository, 100% devoid of compiler/linker trickery). Or a desktop framework that offers UI design capabilities comparable to the introspection-based ones I find in ObjC, C#, or whatever you want to call the home-brew C++-with-reflection that Qt uses.

The best apprach is to have "reflection" (really, access to the compiler AST or IR) at compile time and generate code from this, since that minimizes the run-time overhead.

See Rust's serde for an example of that for serialization.

Yes. And don't just think about how messy the homegrown alternatives are - note how much effort people go to add them in! It's just such a useful thing to have - serialization; logging; UI generation; automatic scripting language bindings - and that's why people bother.