I doN't see it as dark...
out of these only ESPN fighters have some kind of exclusive network deal if I know it right but maybe not even that and they just fight where Arum says so
HBO likes to work with GBP but GBP can appear elsewhere like how Jojo Diaz fought GRJ on Showtime for example
Haymon/PBC fighters can appear elsewhere too as it happened multiple times throughout the last couple of years
Hearn has signed some fighters to DAZN but Idk if they can only appear on DAZN or no but I think they can. For example Maurice Hooker just got signed by Hearn and TR won the pursue bid for Hooker vs Saucedo which presumes that it gonna happen on ESPN and so far no word on Hooker dropping his belt or anything like that.
The market is more fragmented now than 6 years ago in the HBO vs Showtime era but I think it is more free flowing and the terrain changes quicker too, I doN't think that it is harder to make fights ppl want. A Spence vs Crawford takes time either way cause probably both sides banking on that fight becoming some big fight down the line and Haymon has plenty of quality fighters to match against Spence in-house before he would have to go to work with another promoter for a fight which potentially (more so than the other fights...) get his fighter lose.
2017 and now 2018 are some of the best years for boxing in this decade so far in terms of fights getting made so I don't see the reason to be pessimistic now.
EDIT: actually it seems like ESPN fighters are not exclusively ESPN either...
Stevenson's side won the Gvozdyk negotiations and it seems like they gonna go ahead with it and the fight will get made. No words so far about Gvozdyk not being able to fight on Showtime