Is it worth?

In the long run? No, because its extremely likely you will never ever see this player again. In the short run? Yes, because seeing that instant feedback report popup 10 minutes after reporting someone / next time you log in is satisfying.

Unless there is a hidden question behind your question like "does the system really work? cos I can't see it working at all", the answer to your question is always yes.

Cost of reporting a toxic player: 5 seconds. Benefit of reporting a toxic player: Potentially never seeing that player ever again.

I think that's worth it.

had an inting annie toplane a few games ago, post game she was arguing with someone and other person left

We all reported her obv, and in the middle of the argument, the message popped up on my screen that a recent report has etc...

The second after that notification, in the middle of the argument at the most random time, she instantly left the room mid statement.

That meant she got banned on the spot, we all had a good laugh

In theory, the time you're taking to report somebody who may ruin others' games is also being taken by others' to prevent somebody from ruining your games down the line. It's a team effort.

Trolling, unfortunately, will continue to be part of League unless they drastically change the model of the game (ie. abandoning the f2p model in favor of paying for an account up front), which will almost certainly never happen.

Yes. Because eventually consistent toxic players get permabanned. Oh wait, most of those players don't reform and just make new accounts and ruin the new player experience now...

No? I don't know.

Sure, it only takes 10 seconds. Even if it's just a placebo effect, I'd say the simplicity of it makes it worth.

Yes of course.