I mean there’s material evidence out there that pretty well proves it, and Russia has ceased to claim that they’re fake reports.
If the kinzhal missiles were actually “hypersonic missiles” that could maneuver at speed, then yeah they’d be hard to intercept. However, the kinzhal are actually just missiles with a ramjet, meaning they hold a fairly normal flight trajectory and can be targeted by systems like the patriot.
Shooting a bullet with another bullet is basically what all anti air systems do, the only thing that changes is the scaling in the math.