Ukraine is doing that. They have anti-drone drones called Sting

No emp because when it comes to drone warfare cost effectiveness is imperative. No use using a multi thousand dollar drone to down one that is a fraction of that cost.

Russia is pretty much doing the same as well. I just watched a video this past week of a drone of theirs skewering a Ukrainian reconnaissance drone with metal rods until the recon drone caught fire and crashed. The Ukraine war is definitely the cutting edge for drone combat.

It’s called the Metal Gear Mk. II and it’s actually remote controlled using a ps3 controller

They are, they just aren't advertised

FPV drones are anti-everything that moves drones.

Shoot it's LIDAR, done.

Japan was doing that a couple of years ago.

Drones aren't very evasive. Most just fly a set pattern. So yes, you could easily down one with another drone, if you are able to notice it, catch up to it, hit it, and successfully down it. But to effectively do that, you need significantly more anti-drones than drones.

More effective is probably lasers or masers from a ground station. It's a lot easier to hit a drone when your weapon moves at the speed of light. But that still means you need to notice and target it. And with a ground station, you can only counter stuff in the local area.