tell me what to fricking add
this is not constructive in anyway
you're basically saying "this is bad, but i'm not going to tell you how to make it good"
Add small black cubes floating in mid air you bounce off of.
This is a good idea.
You need to, (especially if you're going to keep a plain square battlefield), add more obstacles that are both stuck on the ground as well as ones in the air.
Something that will allow you more tact in fighting than just to run at each other and jump around.
Perhaps add walls and things in random locations which when touched will bounce you away from them, or anything else like that.
Try turning it from being more than just a trampoline TDM, into say, a Jelly Arena TDM. Everything you can touch (perhaps not spawns) will bounce you around.
Clutter it up and such, and then players can bounce around the area using that as an advantage to attack each other.
You could even event it so that some obstacles appear and disappear randomly (or on a timer, rather), so that the battlefield is constantly changing.
It's up to you, you just need to add more content to it so that it's more than a very open/plain bouncey battlefield.