We are only a few months into R so please take this worth a grain of salt! I went through similar emotions when we first started counselling. I felt like we were focusing too much on what was wrong with our marraige and not enough and not enough on the A and WH's screw up. I got really upset at one point and yelled at our MC and WH.
Our MC pointed out that the BS wants to focus on the A but talking about the events leading up to the A (and their role in the breakdown of the marraige) cause them a lot of pain. On the flip side the WS would prefer to focus on the events leading to A but doesn't want to talk about the A itself due to shame. This was definitely the case with WH and I. Now we are working on what our future will be like, creating a roadmap.
While I will never take responsibility for WH's A I have to accept that we together contributed to a toxic marraige. WH couldn't cope with it and decided to turn to someone else instead of coming to me and expressing his unhappiness.
Just my experience, feel free to disregard if you feel it doesn't apply to your situations.