The net result of this is that your typical SAG member who doesn't have the power to demand higher rates anyway based on their own reputation ends up with almost no work because so few productions can afford to hire them,This is false. Pretty much every theatrical film, broadcast or cable TV show, and nationally aired commercial in the US is subject to union/guild scales (and even Netflix has begun negotiating with the unions and guilds.)
If you have a "reputation" in Hollywood then you are making above scale because your agent has the leverage to demand above scale. And if you don't, that generally means you are a background player and you're making minimum scale. And at that level, you have trouble finding work because there are hundreds of thousands of other actors competing for the same roles, not because the productions can't afford you.
If you cast your mind back to the video game voice actor strike a few years ago, for example, you may recall that one of the justifications for that was that they needed more money because many of them were only getting something like one day's work a month on average
Yes, because there isn't that much voice over work in video games, and AAA studios were paying minimum scale for games that ultimately grossed hundreds of millions of dollars.
Mostly because no-one outside of the big triple-AAA games could afford to hire union voice actors.
This is false. The union scale for video game voiceover work was $825/session, no residuals no benefits. It usually takes less than 3 sessions to record all of an actor's lines, so you're looking at a total net outlay of less than $2500 for an actor's voiceover work in a video game. If your studio can't afford that for a game in which voiceover work is important enough to justify 3 sessions of recording, then you're not a studio, you're a hobby. (But on that note, a different, lower scale applies to low-budget games, just like it does to low-budget film and TV productions.)