All relationships are dysfunctional. It's just a matter of degree. Sometimes it's deadly. Sometimes it's trivial and 'sub-clinical'.
Do I need to 'fix' the relationship?
Do I stay or go?
When I change my attitude, my disturbance at the dysfunction goes. If I'm disturbed, my attitude is still wrong.
When I change my behaviour, my part in the dysfunction goes, and a lot of the dysfunction drops entirely or is converted into a less pernicious, more bounded form.
Once my side is cleared up (which is a process, not an event, and requires vigilance and maintenance), I'm left with the other person, and their dysfunction. If they're in active addiction, at a stage in recovery where there are still major unresolved behaviours, or outside recovery and simply odd at times, all I'm left with is the practical side.
Once my head is clear, it's amazing how much of another person's dysfunction, even in close proximity, can be worked around with a bit of reorganisation and negotiation. There are certainly showstoppers (physical violence, real verbal nastiness, haemorrhaging money from family finances) that I would not put up with. I've been amazed at how what appears unacceptable actually proves to be neutral or trivial once my mentality is cleared up.
Is it even dysfunction? Maybe whatever it is is just a trait. My own 'traits' will often appear to others to be dysfunction.
I've never improved a relationship by discussing the relationship with the person I'm having a relationship with (in the presence or in the absence of a third party). I discuss my wrongs and request input on what I should stop doing, start doing, or do differently (although this request is made only to reasonable people!)
Every relationship I have ever been in that has improved has done so because I've done the work myself on my side of the fence.