I don’t think Pitkeev is a good example of how hard it is to change from singles to ice dance, because he was injured. He had no chance to start with. I think he was kidding himself when he decided to try, because he just wasn’t ready to accept the reality that because of his injury he is done with elite competitive sport. But Stavitskaya is a better example because she was healthy and I do believe she gave her best to it, and yet it didn’t happen.
Regarding Yanovskaya/Mozgov and their current careers with their current partners, it seems to me that Yanovskaya is quite tall, so that would limit the choice of her partners. She found a partner (Lukacs) who was far below her skills and I don’t think he is particularly talented, but they don’t have any competition within Hungary so at least Yanovskaya got out of this her trips to Europeans and worlds, so I don’t think she has any reason to complain. She might even feel lucky that Mozgov dumped her.
And Mozgov’s career, well, even though Popova/Mozgov are in theory the better ice dancers than Yanovskaya/Lukacs, because there are at least three much stronger ice dance couple within Russia, it may take a while to get to Europeans and worlds (if they ever get there at all).