The Rust for Linux project

It took me a bit to realize what you were getting at with 'technical debt' but I think I get it. If I understand you correctly, you're worried that the increased features adds to the complexity and thus costs later on to develop on top of a Rust library or rewrite it.

In C, I would argue many things are presented as 'overly simplified' with hidden behaviors that many developers may not consider until it bites you with undefined behavior. The typing system is not very strict which gives many footguns, there's practically no such thing as memory safety, etc. I think you know all this, and you're right that Rust adds features to be safe, and programming under Rust with this subset takes some time to think about how you want a program to function.

What I'm getting at is that it takes time and experience with Rust to be able to formulate an effective and friendly program structure, just like many other programming languages. You wouldn't be expected to pick up Haskell and know exactly the 'right' way to make a web server application, and Rust is no different. There's also never one obvious way to construct a program; sometimes you do need to scrap your current code and start over, regardless of the language used, and that happens less as you learn about the tools you are using.

The additional features of Rust do add more to consider in your design and may add to technical debt later on, but with experience, you gain insight into how your program synergizes with the Rust model and it becomes less of a burden. Likewise, the clearly marked unsafe portions of code, enforced typing model, and lack of undefined behavior remove a lot of time reviewing code and running static checkers against your program, of which C++ does not really remove despite being more 'feature-rich' than C and containing things like templates that Rust doesn't have.