However, if you reduce the language surface it is possible to have something safe and simple enough (IMHO).
For instance, you can say no async, no custom traits and only {Debug, Display, Eq, PartialEq, ...} are allowed for your structs and generics. From limited personal experience that takes away more than half of the complexity of navigating rust code.
You might be able to outsource some complexity to external libraries, but integrating libraries is itself a major headache, and it can lead to security issues too.
However, I believe the being "opt-in" by explicitly marking sections unsafe is the way to go instead of having unsafe by default (which is the only way using C).
You don’t need to outsource complexity anywhere. Rust is fully capable.
I think Rust’s reputation for being hard to learn is overblown. Yes it is probably a little more esoteric than what you’re familiar with but any decent dev should be able to pick it up
This is from my favourite book: In the beginning was the command line.
[0] https://web.stanford.edu/class/cs81n/command.txt , search "HOLE HAWG".
But, people aren't writing K&R C. These days most of them are writing something closer to C99 or C11 and some may be using something newer (e.g. C17) or proprietary (GNU's C dialect) either deliberately or just because it compiled and nobody told them not to.
At that point you've actually given away much of the simplicity, and yet what you get for your trouble is largely more footguns. Trade up for a sound type system and fewer footguns instead.
This makes simple application code slightly faster. That's kind of a reasonable domain for C++ but on dubious ground for C. Where C is superb is talking to hardware and language implementation, exactly the areas the ISO group has chosen to cripple the language for.
Thankfully compilers know about this and provide fno-strict-aliasing et al. Maybe there should be a std= style flag to change to the language subset that doesn't actively try to miscompile your program chasing benchmark numbers.
Next one is what, the C11 memory model? Doesn't take away any simplicity, just defines things better.
In both those cases the K&R C model was very simple. You could decide you love how simple this model is, and when smarter compilers optimise it into a pretzel or other languages are faster that's OK. This code used to drive the serial port, now it does nothing, OK, don't use C to write such drivers. This code used to go real fast, now everybody else is faster, OK, don't use C if you need the best performance.
C89 and C99 choose different, making the language more complicated to keep addressing performance and compatibility. In C99 I can write the fast serial port driver, but it's significantly more complicated as a result. The beginner will definitely get it wrong and explaining why is pretty subtle.
Then C11 says actually you're not writing sequential programs, which was a crucial simplification in K&R C - the programs you can write do one thing at a time, in order, and then maybe stop. The memory model in C11 is needed because it says actually your programs might do more or different things at once.
Now, in reality by 2011 lots of people were writing C that's not actually sequential - after all SMP Linux long pre-dates C11. But those weren't legal C programs, they're GNU's dialect and so all bets are off. Nobody is claiming Linux is simple.
So C11 definitely isn't the simple language for a 1970s computer any more. C11 is a competitor with C++ or today Rust. And it doesn't fare so well by that comparison.
C11 atomics would have been much better if they'd standardised existing practice instead of inventing something based around the application centric design C++ was inventing. It's nice that there's an acquire/release scheme one can reason with but a real shame that they conflated it with type annotations.
They were far less homogenous in the early years. Today you have a octet addressed little endian integer machine, with ieee float hardware and a small vector unit. Maybe you have two different instances of that on the same address space, but probably just one.
I think reasonable argument could be made that the complexity in modern computing is primarily self inflicted by software engineers.