My husband is Russian. Left before the curtain fell, just nissim that he and his parents escaped. Life was not easy then. Now it is supposedly easier, but there is still a lot of antisemitism and, to be honest, even though the current government is not Communist, there are still issues with respecting human and religious rights. The people who were born and grew up there may very well be keeping mitzvos now, but there is probably still an element of fear of being caught and having problems because of that. They may not know what it’s like on the outside. Many are very happy after they leave. It’s not easy to stay and not necessarily easy to go.
As far as everything that Hashem does is for the good, then your concerns about the “pain that may affect other aspects of one’s well-being, currently and intergenerationally” (not sure I understand what this means), it means that even the pain is good. If a person truly understands that this pain is for his/her growth and does not get bogged down in it, then it will be used as a stepping stool for further growth in areas down the road. Not all good seems “sweet” to us over here, it can be painful, but a person has to ask Hashem that they should see the sweetness of it, hopefully while they are going through it, but if not then, then afterwards Hashem should give them clarity why they went through such an experience.
Remember that Yaakov had to go down to Mitzrayim. It was necessary for him and his 12 sons to be in Mitzrayim. But Yaakov did not want to go. Yaakov wanted to be a “ger” but stay in EY, but HKBH said, no, in Mitzrayim. Even when Hashem sent a hunger, he stayed behind and sent his sons to Mitzrayim to get food and bring it back. Hashem realized that it would take more to get Yaakov to go, so the whole story of Yosef going to Mitzrayim happened in order to bring Yaakov there. All this in order to fulfill all of the promises Hashem made with Avraham Avinu. We cannot think that we know better.