You can get hired for guild work as a non guild member, usually you join the guild after though.
But the number of times I've heard directors and such tell stories about how they wrote a line for a non-speaking part as a favor to the actor in the role, solely to allow them to get their SAG card, is disturbing.
It's indicative of a high degree of gatekeeping.
It’s great when you’re in but if you don’t have the connections to get in you can find yourself on the outs for years.
If a SWE guild can find a way to eliminate the nepotism and create a meritocratic way to get into a guild…