Well there were a lot of missed opportunities in season 3 that could've been hit with more teamwork between Matt, Karen and Foggy:
One is the prison fight. I know the series is constrained by time, but they should've explored the fallout from that scene in more depth, its impact on Matt, and maybe let others in on what happened. They only really brought it up once with Nadeem questioning Foggy. But legally, it could have sooo many implications. I think Matt's actions here should've had some consequences for Foggy by causing Foggy to end up being put under investigation on Fisk's direction. I'd have lived for a scene where Foggy chewed Matt out for stealing his ID and using it at the prison. (In fact, come to think of it, Matt never told them about the visit he paid to Fisk in prison in season 2 after Frank escaped either. And that visit was the whole reason Fisk orchestrated this whole trap for Matt in the first place)
But as it stands, the prison fight and several other moments in season 3 basically exist in a vacuum. Season 2's writing had the same issue, where key details would often be left out of conversations in order to simplify conflicts and streamline the plot. (Like when Karen found Elektra and Stick at Matt’s apartment, for instance: in the next episode, she goes to Foggy having only noticed Elektra in Matt's bed, because the writers felt that it was easier to write Karen being angry with Matt for seemingly cheating on her, rather than contend with Karen, a talented investigator, interrogating Stick at the apartment and discovering Matt’s secret five episodes earlier).
Season 3 arguably actually did a much better job with building tension than Seasons 1 and 2, but it came at the expense of some subtle character beats. More teamwork would've also allowed us more insight into how Foggy, Karen, and Matt were actually coping with being separated from each other so much. It would've solved the problem of where it seemed like there were too many moments where everyone just seemed to go lone wolf and got nothing done. Giving more interaction between the characters would've also helped in the later episodes where things felt a little rushed (as it goes, it seems like only three days pass during the period from episode 9 to episode 13).
Admittedly, I'd say a lot of these missed opportunities were a consequence of the structure of season 2 and The Defenders. This results in a lot of threads in season 3 that would've been better if they were resolved earlier or differently.
For instance, Karen's confession to Matt about killing Wesley. It would've made as much sense, if not more, to have her do that confession in season 2 in the middle of Frank's trial. That would've solidified the development of her season 3 arc. The confession between Karen and Matt in the crypt also rehashes a lot of the beats from the exchange Matt and Frank have on the Blacksmith's boat in season 2, without the nuance that would have provided greater dimension for the exchange. Karen was changed by killing Wesley, and that's supposed to make her stand as a validation of Matt’s faith, since she has committed to being better in spite of committing bad deeds in the past.
That the writing in her confession to Matt was framed around why Karen didn’t tell Matt or Foggy rather than the circumstances under which Karen killed Wesley, also seems to be the writers trying to avoid discussing the fact that it was an act of self-defense. Making the order in which Karen confesses to people about Wesley be Matt, then Fisk, then Foggy, or just writing the scene with Foggy differently, would have allowed for the conversation to tackle the more important questions of Wesley’s death.
Karen's confession to Matt about Wesley also highlights another flaw which is that the show rarely gives Matt enough space to process revelations. Charlie Cox actually complained in some post-Defenders interviews about Matt never getting room to mourn Stick's death. The same goes for Father Lantom's death here in season 3, which is kinda overshadowed by the Wesley confession and by the first half of the episode being Matt and Karen hiding from the feds, which too falls under this. Putting the Wesley confession here--and so late in the season to boot--kinda defused a lot of the tension from that revelation. And Karen is just telling Matt "trust me, killing people is bad for your soul" without really communicating anything meaningful for him to understand. Telling him onscreen what she did to Wesley and why, would help him to know better. Same for her telling him about her brother.
It would've made more sense for Karen and Matt to flee to Matt’s apartment so they could then talk things out, so that Matt could properly mourn Father Lantom, and he and Karen could talk out the Sister Maggie reveal and everything else. (It doesn’t make sense that the Feds don’t ever check the basement again after the initial search)
