1. Dems - Trump "attempted" to coerce the Ukrainian president and that is an impeachable offense.
2. Rs - You can't know the President's state of mind regarding what he was asking. i.e. Was he genuinely concerned about corruption or was he purely trying to hurt a potential political opponent.
Both are plausible and as you say, probably not enough to sway anyone either way.
I do think that #1 is the only path the Dems have since ultimately none of the requests materialized. I also thought Taylor had one main chink in his armor. He stated definitively that he "clearly understood" that the quid pro quo was a precondition for releasing aid or allowing a White House meeting. That ultimately wasn't the case, so his "clear understanding" assertion falls apart. Again, tough to get inside the President's head.