Personally, I do think it is a double-edged sword. On the one hand, I don't think there's anyone who could match Karen in terms of running the office. But the journalism career is a good fit for someone as inquisitive as Karen, so I could also see why it would be considered a big step back for Karen to quit her journalism career and go back to Nelson & Murdock unless something drastic happened that convinced her that leaving the Bulletin would be the right thing to do. So obviously using her journalism strengths would be a more logical choice than backpedaling her career just to maintain a status quo. Or (unlikely), Karen comes back part-time until they can find a permanent replacement for her / she interviews potential replacement candidates. (Plus the power imbalance that would come from Matt and Karen dating, since I'm pretty certain Matt/Karen will be the romantic pairing for Matt during season 3)
And yet, Nelson, Murdock & Page working together is such an iconic trio that I think it'd be impossible for us to get used to anything else (I'm still kinda bitter that The Defenders didn't give us any scene of Matt, Karen and Foggy all on-camera at once; we got Matt-Karen, Matt-Foggy, and Foggy-Karen). And this impossibility to get used to anything different is key. So even if Nelson & Murdock does get back together after everything that's happened since The Defenders, what would we expect them to do, just hire another receptionist? Or just reopen with no receptionist/secretary/whatever at all? Because like I said in my "Was dissolving Nelson & Murdock the right thing?" thread (you'll see that I did borrow a lot of my old points from that thread), although there is such a thing as journalists who hold down two jobs, Karen does not seem like the kind who'd work full-time for the Bulletin and also have a part-time job at Nelson & Murdock, or full-time at Nelson & Murdock while also writing part-time for the Bulletin.