Most of the journals (we can say all journals) consider submitting the manuscript to many journals in the same time as illegal act. They consider that as a waste of the voluntary work of the editor and reviewers.
However, authors may get their papers rejected after waiting a lot of time (more than a year in many cases), which makes it difficult to get published again.
In some cases, the reviewers just skim the paper and write the rejection, even they are not working in the same area.
So that why cannot review process be a paid process? It can have a different fee other than publishing fee to give the author the right to accept publishing it or not.
I know that will result in a big overhead on journals because the authors will submit their papers to many journals and then withdraw all the submission, except one.
After all, what is the best system for that?