Ugh, tell me about it. I read somewhere that pothos roots take their sweet time because they're building strength for soil. The article suggested using a clear glass so you can see progress, which just makes the wait more painful. My last cutting took a full month before I saw anything.
Totally agree with what william_black said about weekly water changes. I started using a rooting hormone powder on the cut end and it made a huge difference. Honestly, I saw roots in like two weeks instead of just staring at a sad leaf for a month.