Sounds like you played some shitty servers my friend. I'm sorry to hear that.
Quite the opposite - I've played on most of the best servers. The thing is, the better a server is the more people use it, and the more players there are the faster the server gets choked with old players that left, old factions that died, old blueprints nobody wants and old ships and stations. Good servers clear this out (by resetting the universe every month or 2). Bad servers don't have so many players and/or don't clear any of it out.
Hopefully one day maybe, StarMade might keep track and "auto-delete" things that haven't been used for 30+ days to keep itself clean. It currently doesn't.
Now you are confusing me can plays download their blueprints off the server without me or do I need to give it to them. I assume anyone can locally save it?
This should've taken you about 30 seconds to test for yourself. "ALLOW_UPLOAD_FROM_LOCAL_BLUEPRINTS = false" only disables uploads. Downloads are not uploads, so it doesn't disable downloads, and players can still save their work (and upload it to someone else's server).