This is a weird take. Rust is very popular and is the current heir apparent to C for systems level stuff. It’s a great choice to start a new DE/toolkit.
As for the rest, you’re right the end user doesn’t care about the language their graphical app is in, but the developers fielding their bug reports and making fixes/features sure do.
For XP, the machine KVM presents as may be too new, but that isn’t an issue with non-virtualized QEMU.