I’ve had the same reaction. We’ve seen this play out in other language eco-systems (Java - JAXP, javax.validation, JPA, etc all ended up with a de facto single implementation) and the idea of pluggable implementations sounds appealing but rarely pays off. The price that Rust paid for this abstraction - which in fact ended up not being useful as tokio is the only reasonable choice - was high in terms of requiring ugly (to my eyes) changes to its type system.

Tokio is definitely not the only reasonable choice. I use embassy[1] on microcontrollers (the Pi Pico and ESP32 in my case), where tokio can't run.

[1] https://embassy.dev/

There is no price to pay on the type system that was imposed by tokio. I assume you're saying something like "I have to add 'static in generics" or something?

It has absolutely paid off, there are many people not using tokio.