I feel a lot of that probably isn't conventionally achievable since C++ covers a lot of situations with different needs, but if 20% of the functionality could cover 80% of the needs at some point I think it'd be great for the language.
One thing to remember though is that there are two things at play here. The library writers tools, like TMP, and the users. The users can do a lot and never worry about SFINAE/tag dispatch. The library writers use it to allow the users of the library to have a potentially very simple experience.
Also, Greenfield C++ can be way different than pre 2011 C++. The cost of things that people would work around has gone way done to zero in some cases. Like returning a value from a function is like constructing it in place at the caller. So that takes away a need to use the heap to allocate it or to copy it when you return it.
For example, in template metaprogramming we can get rid of tag dispatch and SFINAE thanks to static asserts, constexpr and if constexpr.
Likewise you might decide to shot your code with C style arrays, or use the STL data types with bounds checking enabled instead.