Ending TLJ with no explanation for this mysterious phenomenon that the characters themselves call attention to as a mystery is a far bigger problem, as it leaves TLJ’s own story unfinished. It’s especially bad since TROS doesn’t actually answer the question; at no point in TROS is it explained how Kylo and Rey became linked, they just pointlessly and confusingly give the phenomenon a proper noun.
The thing about Star Wars is that the movies are supposed to tell one story through the entire trilogy. Of course the sequel trilogy miserably fails at doing this. But my point is that leaving something up to interpretation at the end of one particular film is not as big of an issue as you say it is since it is one story across three movies.
As for TROS not answering the phenomena, I think that’s kind of the point. I like the dyad concept because of its mystical and unexplainable aspect. It’s like the Force knew that allowing a dyad between these two individuals was going to result in bringing balance back.
“The Force works in mysterious ways”