a question about Skype (etc.) groups It is easy to find a real friend here. (and I'm more interested in this actually! A real friend is a treasure, a language is just a nonsense)

It is less easy to find a partenr for regular practice: most people aren't good at scheduling things. I'm not good at scheduling things.

A reasonable solution could be an "instant conversation" club. 
A group of, for example, Vietnamese learners of Korean and Korean learners of Vietnamese create a group in any app that allows groups. When you want to talk you ask if anyone is available next hour and have a session with the first guy/gal who answered.
Ideally there also should be availability log, helping people to know which time they can meet whom.

It seems though that people's experience with groups is mostly negative.

Question 1. for those who tried groups.
What goes wrong? Why doesn't it work the way described above? Or no one ever tried to organize it this way?

This question came to my mind because of this guy:
https://www.italki.com/discussion/205432
He has 7 hours a day of Russian lessons and hopes to be fluent in 6 months and he needs practice. Of course many people will respond to him. But likely he will fnd it hard to have a partner each time he needs a partner due to scheduling issues. 

Question 2.
Even more reasonable solution would be "instant conversation" option on a site like Italki (even though a "group" could let you have a specific kind of people in your club, maybe already friends).
And well, there are apps who offer this functionality. I never tried them. What goes wrong in such apps?