If you build something great in your free time and decide to give it to the company you work for you are a fool...
- innovations may require significant resources (think data or compute)
- making a dent in the profitability of a multi-bn $ org should enable a very comfortable life unless you're wasting your hand (in which case you probably wouldn't make it on your own either)
Life does not work like this, the world isn't about "should" it's about "is" and "can".
So if you create something that makes the company 10% more money, at best you can expect a promotion and a small one time bonus that is a fraction of a percent of that 10% recurring revenue growth you just generated for the company you work for.
That is the best scenario. The alternate scenario is verbal recognition with 0 reward and if you work in a truly dysfunctional organization you can expect outright retaliation at some small frequency.
Core assumption: be visible and associated with profit -> good things will come your way.
How much this works will depend on your hand and the table. Personally, I don't feel drawn to dysfunctional/bloated [...] environments at all and have no FAANG experience, so I can't claim to estimate the agency in those environments, but I would assume it to be >0.
[0] https://www.kalzumeus.com/2011/10/28/dont-call-yourself-a-pr...