The F-35 isn't inferior to many other aircraft as far as raw capability goes. Really only the F-22. Nor is it expensive, at least the F-35A (I'm speaking of the initial cost, not sustainment which may or may not be a bargain).

The F-35 is the only genuinely stealthy aircraft any country outside the USA has access to (other than China, and the efficacy of its stealth technology isn't known). F-35 stealth is a game changer, as seen in every exercise in which they're involved.