gcc-ia16 and OpenWatcom are both modern compilers that generate as good a set of code as any compiler ever did for Pentium and older processors. But using a higher level language like C means there’s more than one compiler that can compile your DOS. That’s a reason to be hopeful if you’re a DOS developer.

The compilers have probably got better but the C language has definitely bloated since the 80s

constexpr code and move semantics didn't exist until relatively recently. These are steps towards less bloat and more aggressive optimization. They also can elide gratuitous copy construction.

There are a lot of these little optimizations that are found in modern compilers that you could only dream about in 1991.