One major difference is that Ada was created at a time when most military computers were single-core with in-order sequential execution and no cache. Although limited SIMD existed, any other concurrency was very coarse-grained. That’s the underlying execution model for C, Pascal, C++, etc.
Rust was created to address the complexity of multi-core processors with multi-level cache hierarchies where computational efficiency may require much concurrency. In my experience few humans are capable of error-free design and implementation of highly-concurrent systems unless they employ tooling that flags their errors in conceptualization or implementation.
Just the presence of well integrated Algebraic Data Types (ADTs) makes an incredible amount of difference. They are used to represent errors in a meaningful and easy to understand way (Result<T>), are used to show that a function may or may not return a meaningful value without needing a garbage value (Option<T>), and the optional case can even be used to wrap a null pointer scenario in a safe way (Option<Ref<T>> being the closest to a literal translation I think).
That's just one small feature that permeates the language. Whatever the opposite of a death-of-a-thousand-cuts is, Rust has it.
Writing code in Rust makes me feel like I have an obligation to make code as fast as possible in a way other languages don’t, just by surfacing the costs better. Sometimes I need to remind myself that actually it’s fast enough already.
I used to think of programs as execution flowing and think about what the CPU is doing. As I moved to rust I started thinking a lot more about memory: how the data was laid out in memory, and how ownership of different parts of memory is given to [different parts of the program] at run time.
I like that one since it's in some ways a modern take on a classic:
Show me your flowcharts and conceal your tables, and I shall continue to be mystified. Show me your tables, and I won’t usually need your flowcharts; they’ll be obvious.
– Fred Brooks, The Mythical Man-Month (1975)