I would like to take a moment to point out some things that might help everyone get along just a little bit better. Also, I'm an engineer, so I like lists. Please read the following list of things you can do to make everyone's life just a little bit easier in regards to mumble.
1) Use push to talk.
2) Don't interrupt. If someone is talking, you wouldn't talk over them in person (right?) so don't do it in mumble
3) If someone is in the middle of something, consider finding a different channel, or consider asking if it's a good time to talk.
4) If there is a communication heavy game happening (ie, Rocket League / Overwatch) consider a different channel for each team.
5) "Drunk shenanigans" is fine, but it's definitely not the default.
If you would like assistance or a room made for any of the above reasons, there are several people who are around who would be happy to help you.
It seems like this has gotten worse over time, and especially with Overwatch. Its a 6v6 game, and having two separate games going in the same channel makes it difficult to effectively strategize. Some people have trouble with an overload of audio information.
There are TONS of ridiculously named channels. Please take advantage, and please don't feel hurt if someone asks you and your group to find a different channel for your conversation
You can take voice activation from my cold dead fingers. There's no such thing in person after all.
So long as you aren't transmitting typing and other sounds it's not an issue.
Honestly though, it becomes a habit so easily. I'm happy to help with shortcut advice and setup.
I had push to talk set up for years, but I noticed an improvement in my play when I finally switched. I just have a quick mute button on my headset that I apply liberally.