I have worked at Meta my entire career (~5 years). I know that Meta is pretty "startup-ey" among the Big Tech companies, but I imagine that it can't mimic startups entirely and there's unique learning value startups can offer. Does switching to startups give big value to career development?
In a startup, your learning and growth will depend a lot more on the people you work with.
In a larger company, the people are still important, but you can also supplement your learning with things like architecture meetings, planning meetings, and better documentation.
Specifically for career growth, I usually use this metaphor:
Think about learning to swim. Big tech companies hire the best swimming coach to teach you. The coach has successfully trained Olympiad medalists in the past. The swimming technique they teach is the best of the best. There's just one tiny problem: There are so many people learning to swim the swimming pool is full and has a long line.
You've been learning about swimming with this coach for years. You learn everything possible from the books. You practice every movement on the land. You are just waiting for your chance to get into the water. You are frustrated that you haven't received the credit for swimming because you haven't demonstrated swimming in water. You believe you can totally swim.
This is big tech. You believe you have the skills and deserve that promotion. You just need an opportunity but that opportunity never comes. It's so political and unfair!
On the contrary, nobody knows swimming better than you in a startup. There's no peaceful and safe water like in a swimming pool. There's a ravine. Water is rushing through. Swim or sink. Jump in and see if you can get out alive on the other end. If you can you are way ahead of the other person waiting for their swimming pool access. If you die, nobody remembers the dead bodies at the bottom of the water.
Meta's culture is already leaning towards swim or sink. However, it's too big and the bottleneck for supporting employee growth becomes opportunities. Meta is (or at least used to be) very generous at spending money on enabling employee growth. You can learn from the best. You just need to have access to opportunities to practice your skills.
Startups don't guarantee better outcomes. There's a chance but you have to accept the risk of getting a worse outcome.