> If publishing the most papers is the goal why do we even need journals?
For discoverability. Someone's trivial finding may be someone else's key to a major breakthrough, but little good it does if it can't be easily found
This isn’t being realistic. The major benefit of these is peer review. You aren’t going to have enough people to peer review the work of a massively open and public publication system.
On top of that the chance of finding something as you suggest becomes that much more difficult. Smaller findings get published now in a more controlled scenario and get lost in the stream.
Major journals are a net positive for surfacing important science.
In my field, arXiv (free preprint server) is actually much more discoverable than journals. It tends to be on top of Google searchers, many people (myself include) check it out daily, and few people even check journals (why would you check dozens of different ones if everyone posts their work on arXiv?).