Find good managers! Or groom them. Whichever. Just make sure you have good managers.
I see endless posts about recruiting, and I see tons of posts about engineering culture, but I almost never see posts from these same sources about the nitty gritty of how to evaluate and grow leadership and people management skills. Ironically, I see a lot of that from MBA programs.
Actually getting good management in place is extremely hard to do and does more for talent retention than almost everything else. For every company blog post I've read that talks about scaling the organization, including Stripe, I also hear corresponding horror stories from friends and acquaintances who are leaving because they hate their manager and because their company isn't doing anything about it.
Sure, it's relative, on the grand scale of managerial quality I'd wager that Stripe is on the right side of average, but I'd really like to see more focus on scaling leadership.