Rust is built on lifetimes but the compiler could definitely infer them better. Not only from my experience, but all attempts to introduce coworkers / anyone else to Rust usually meets a "this 'a thing is ugly and awful and I hate it".
Really it was more a design decision on the language part than something it was "built" on. In 99% of cases the compiler can identify where exactly you need to annotate lifetimes to sate itself. They are only there for explicitness. Tagged lifetimes will help a lot with this, because it is much more intuitive for anyone using any other language to say "ok I need to say result R lives as long as argument A that makes sense" vs "stick an 'a on everything" and have functions that have nothing to do with generics looking like generics to the average joe.
I know I personally have written function signatures to take (or return) owned data in Rust just to avoid having to lifetime annotate the whole thing. It is just a chore that most of the time is just boilerplate to "make it obvious" to readers of code, despite almost every situation I see lifetime annotations I can straightforwardly understand that the & in the return is lifetime bound to the & in the arguments or the struct field it comes from.
