Marvin Lewis was coach for 16 years with a barely .500 record (131-122) and was 0-7 in the playoffs he made it to (his last 3 years were playoff-less). He was .627 in the 5 consecutive years they made the playoffs.
I'm not saying this has any impact on what happens with McD if he doesn't win a championship in the next few years but the fact he has been to the playoffs 4/5 years compared to Lewis's 7/16, he's going to get a lot of leash unless there is a catastrophic collapse over the next few years.
And no, Bengals didn't have Josh Allen on their team before you make that part of the reason he should be fired if they don't win a championship.