Everyone's telling me I'm doing great - How do I get actionable, constructive feedback?

First, I recommend checking out discussion around maximizing the learning from your mentors: "How do you get the most out of mentorship?"

In a nutshell, feedback is something you need to be proactive with. Be as specific as possible with what you want feedback on, and ideally ask about something recent (e.g. "I felt like the meeting I just ran could have stayed on track better - You were there, what do you think?"). We cover this strategy in-depth here: This Is How You Get Feedback - Making The Process Smooth

This same proactive feedback concept also applies to code:

• For any commit you write that was of decent complexity, I recommend detailing your approach in the context section of its pull request.
• Highlight all the approaches you considered, and invite reviewers to comment on whether they think you chose the right one - You're essentially nudging them to play Devil's Advocate against you.
• On a similar note, if you feel like your commit isn't perfect, you can self-comment on the parts you feel like were messy/hacky and explicitly mention senior+ engineer reviewers to leave their thoughts on it.

Rahul and I talk more about the above code review feedback "tricks" in our video here: Quick Tips To Get Higher Quality Code Reviews Faster