I'm forced to use the buggy Reminders app, because Siri only supports creating reminders with Reminders. Apple refuses to support anything else than Apple Music, which means I can't use Siri for music. (Yet, when the 4S was released, it only took weeks until I could control Spotify with Siri using jailbreak). I can't use Siri for navigation either in any form ("Hey Siri, when does the next train leave from here?"), because Apple has never provided public transit or good navigation in Sweden, nor announced a timeline on what year that might happen – and of course, Google Maps can't use Siri. And even if it could, Siri does not gracefully support foreign words such as addresses.
I could easily love Siri if Apple would stop gimping it by tying it to other subpar products.