So I remember bringing this up earlier this year here on this thread:
At the time I was feeling overworked and frustrated on a project that wasn't paid and was taking away time from my own stories. But the majority opinion was that writing and art was 50/50 and so I was trying to see it as such. Got better when I talked more with the writer and it really did feel like he was putting in a good chunk of work that 50/50 didn't bug me. He was a pretty good writer, didn't really have a reputation or anything like that, but I could tell he was putting in the effort and also communicated well.
However, the art was taking a loonnng time and alot of labour. Since I wasn't doing story I went a bit above and beyond what I could probably handle at the time. It got received well but there wasn't going to be a return anytime soon. Also, my financial situation at the time took a sudden downturn and I needed to start taking paid jobs. The writer valued my work so far but couldn't pay me, and so I needed to move on.
I still do collabs, but now I'm more realistic about what I can actually do and the value of my work, as well as having decent expectations of the writer. If its 50/50 possible future rev-share, I'm only going to put in the time/effort that I can reasonably expect from myself given that set-up. It's not like I don't have my own stories to work on.