getsiu
It doesn't work very well, unfortunately. Those willing to pay usually are the most interesting part of the audience for ad providers, so it's difficult to compensate that loss by a reasonably priced 'ad-free' option. You probably would be surprised if you knew how much your attention may cost. Targeted ads created a market where everyone pays proportionally to their spendings. I'm not saying it's a good situation, but it looks like that's a local optimum rather hard to leave.
What bothers me is that huge companies are more resilient to tracking and ads restrictions, so that fight may further speed up centralisation of the internet. I would personally prefer the chaotic old-school world wide web with ugly flashing banners instead.
It seems to me that the most common reason for leaving the company is immigration, which has nothing to do with Yandex itself. All my ex colleagues who left Yandex work abroad at Google, Facebook, MS and etc. Also I've seen many very good developers who cared a lot about their products. So my impression is somewhat opposite to what you described.