Rust isn't a complex language by the standards of languages like C++. Complexity arises by features that work together in surprising ways. Rust has a medium-large amount of features (similar to Python (though obviously with a more imposing learning curve than Python)), but those features tend to compose very well, which keeps complexity from ballooning.
It is true that Rust is competing most directly with C++, but "less complex than C++" might be a true statement about every single language in existence that has more than a dozen professional users.
