Lazy evaluation in C++14/17 - just lambdas or also futures etc?

I just read:

Lazy Evaluation in C++

and noticed it's kind of old and most of the answers regard pre-2011 C++. These days we have syntactic lambdas, which can even deduce the return type, so lazy evaluation seems to boil down to just passing them around: Instead of

auto x = foo();

you execute

auto unevaluted_x = []() { return foo(); };

and then evaluate when/where you need to:

auto x = unevaluted_x();

Seems like there's nothing more to it. However, one of the answers there suggests using futures with asynchronous launching. Can someone lay out why/if futures are significant for lazy-evaluation work, in C++ or more abstractly? It seems as though futures may very well be evaluated eagerly, but simply, say, on another thread, and perhaps with less priority than whatever created them; and anyway, it should be implementation-dependent, right?

Also, are there other modern C++ constructs which are useful to keep in mind in the context of lazy evaluation?