It's due to these countries if they are deemed to allow any of their representative sit in a table with other representatives for peace talks. The UN is in the midst of it as the mediator for all of the peace talks that shall be done. But if the other party isn't willing to cooperate, we won't see them sit in any of them and have a meal together. There is no solution to a country that doesn't want to cooperate despite with all of the efforts and coordination done by them. As said, they're not perfect but we shouldn't deny that they're doing its job.
You are right on that. It is significant that the UN also offers a platform, representatives of such conflicting countries can get together. Without said platform, there would not even be an opportunity of dialogue. Naturally, peace talks can be effective only when the people on both sides are eager to collaborate, and unfortunately, it does not happen constantly. Yet, it is an essential measure to have a neutral ground to be discussed, even when the dynamics is slow. It displays that at least they are trying to seek solutions and this is better than having no dialogue in the first place.
It takes two to tango and it takes time for all concerned countries to start talking about it. But if the other has a grudge to the other party and even after the talks, we'd see if there's a betrayal on their end. We've seen Ukraine's president Zelenskyy went to the US to talk to Trump but he seemed humiliated. And the upcoming one is Trump and Putin in Alaska, so, there could be a positive development for all concerned parties in agreement. While the UN and push for all of the countries concerned onto this deal because they're more concerned of the affected citizens than what these leaders have to say.