Unfortunately, no — Area 51 would not be more effective without down-votes under the current process. Yes, we might be able to push more proposals through, but without a means of expressing disagreement, offbeat (and sometimes frankly bad) ideas can only trickle upward even with only a small contingent of users who may be unfamiliar with the underlying issues or what will actually work in this process.
By our own admission, Area 51 is a somewhat quirky and nuanced system to work with. It's often not easy for incoming parties to grasp how or why the proposal process works… or what types of questions will "work" on a Stack Exchange Q&A site. But a new or improved process is not possible right now, so the choice was to cope with the admittedly less-than-ideal experience if it meant keeping the service available for those who can successfully navigate it.
I see the down-votes. I can and do contact users who seem to be operating in bad faith. But more often than not, seemingly unjustified down-votes are at least somewhat warranted, given the current process. Such votes are typically a curt reaction to something that doesn't quite fit. There's typically nothing inherently wrong with whatever the recipient is trying to post, but when questions like "Is a cashless society a good thing?" are posted (just an example), it is often difficult (and sometimes draining) to fully covey exactly why such questions (or feature requests, or promotions, or suggestions) aren't really a good fit… every time it comes up.
The process IS getting better, though. Small incremental improvements have alleviated a huge percentage of the confusion and misguided efforts from this process. I'm about to integrate a lot more instructional guidance about what to look for in a productive proposal (no ETA yet). I am aware of the issues you raised in your post, but disrupting or eliminating an essential part of what balances this system which <quote> "…still works somehow" simply is not possible at this time.