What to do to provide feedback when it is needed but not requested?

If you feel like something can be better, you should speak up - That's part of the open culture at Meta. The caveat I would add is around prioritization. If something is unimportant and there's a way to improve it by 5%, then that's probably just not worth your time to bring up. Meanwhile, if a teammate is presenting a system design for a critical project, you should be completely unafraid of sharing feedback, especially as an E6.

The main thing here is how you provide the feedback. Go through my lesson about it here in my Effective Communication course: https://www.jointaro.com/course/effective-communication-for-engineers/effective-communication-guide-part-5-giving-feedback/