Keeping boss fights unrandomised is a really interesting idea and an elegant solution to many of the problems inherent in randomisers. However, for me at least, seeing the crazy combinations on opposing trainers' teams (especially in boss fights) is the best part.
Overall, I think people just need to moderate their expectations about what a randomiser can deliver in terms of satisfying gameplay. It's less an equally viable game mode and more just a neat little side-project that's fun in small doses.
Of course, there are ways to create a more structured Pokemon randomi