A bigger problem would probably be that consumer routers are built as quickly and as cheaply as possible. Every megabyte of additional storage costs cents on the dollar extra and even that gets shaved off if possible. All the router security research I've seen done by well-intending academics got turned away by manufacturers because they don't want to ship additional software in their already-constrained images.
Rust, on the other hand, has all the downsides of static compilation combined with the library bloat we see in nodejs.
For a home router to run Rust, you'd probably need to compile the entire router into a single firmware image doing everything or you'd need to build an extensive dynamic linking system on top of the existing Rust infrastructure. Or, alternatively, convince the router manufacturers to spend another dollar or two on their EEPROM, but good luck getting them to do that.
Finally, the core parts of the system (the drivers running the DSL/cable/fiber/wifi hardware) are all closed source blobs that the manufacturers (be it Broadcom, Intel, Cisco, or Qualcom) need you to load and execute, usually written in a language like C with none of the benefits of Rust. Unless you want to rewrite the drivers in Rust (and good luck to you reverse engineering all of those and fighting the cease and desist letters you receive), the core parts of the system are still vulnerable as all hell.
The configuration can be made reasonably simple; OpenWRT has a GUI that can easily be dumbed down enough so normal folk can use it. Even in consumer routers, a lot of configuration is still dumped to text files already, anyway.