I noticed Italki website became less popular then before. What do you think about and what is the cause?
Looking at Alexa's statistics, I don't see any evidence that italki is less popular than before. Take a look at the chart. It's one of the top 10,000 sites, it is currently #6,874, which is 2,778 higher than it was three months ago.
No, I don't work for italki. And I expect to see a visible drop when they shut off the "classic" site.
1.wrong utilization of the site.