I sort of feel like most people don't stay at a place long enough to get cohesion or see enough they don't want to stay in the first place, good people chase better job offers (and congratulate themselves for doing it on their own), less good may stick around longer because they can't move but also are more focused to just stay employed.
Software is also a broad industry in terms of the type of deliverable work (e.g. think buy-once software vs. SaaS vs. in-house industrial controls), skillsets, and environment. It's also hard for me to even conceive of what a typical fast-moving startup would look like full union. Lines between ownership and management and labor can get very blurred.
Is the best hope to look at things like the entertainment industry which are also extremely fluid, but have been very successful? Do we need a long-term period of dev salaries coming closer to median pay (which we might be entering now)? Do we need to better address the ageism monster?
The games industry recently made some real headway [1], which I applaud. Maybe focusing on smaller sectors is the right approach.
[1] https://www.gamedeveloper.com/production/industry-wide-union...