I know I have mentioned this in a couple threads but I wanted to highlight it:
You can't playtest a system unless the system is complete (ie fully playable). It is one thing to ask the public to playtest a new class or race or whatever within the context of an existing system, but it is inefficient and counter productive to playtest discrete changes inside a system a couple Olathe a time.
To companies looking for playtest feedback from the public:
Put out a complete, stand alone playtest document and then give us the time needed to actually run it long enough to give useful feedback.
Counterpoint: You are using the wrong metrics.
The efficiency that matters to the game companies (and should matter to us as well) is designer efficiency. Expecting designers to design a full, playable system without feedback, and then go and have to rework and redo large swaths of the system once they have the first feedback, including ripple and second order effects, rebalance, again put out a full system (after a long wait because of how many interlocking changes would need to be made against a full system), for a second round of feedback, is just horrible, crazily, ridiculously, and business-unsustainably inefficient. Plus it assumes that players will test everything (high level play?, subsystems X, Y and Z, both solo and in conjunction with each other?) so that it doesn't have rounds of feedback and then have some of the base assumptions challenged and make fixes with big ripple effects again. Oh,a nd that all of these players are willign to spend three hours filling in a complete system survey about every aspect, with equal attention to detail for the whole thing.
Instead, putting out a few systems that hang together, like "try these combat bits - they don't include psionics and have simplified terrain and no mounts, vehicles or starship combat, and only these few pregens and those four monsters we hope the math works out on, but we want to see if our basic encounter subsystem works and runs fast and is fun", then doing it again or again.
In other words, putting out a minimum viable product to get feedback on that before building on it.
And that's for a whole new system, not something building on something like OneD&D is building on 5e where we have a "good enough" framework to test parts.
Also, there's a whole lot more player hours to be had then designer hours.
In software design there used to be a model called waterfall, where you design and build everything up front. It's been depreciated by real developers where the business has allowed for a variety of more flexible development methods designed to keep putting things out and getting feedback. Follow the entrepreneurs - "fail fast".
Valuing player efficiency over designer efficiency causes playtest delays or removes playtests entirely due to unreasonably long development costs, which are in turn due to massive rework efforts and the slow feedback cycles those engender.