Nobody will take care of your career like you will

The reality as you get more and more senior is your manager will most likely have more reports, and almost certainly have more problems under their scope. In fact it gets to the point where they are almost guaranteed to have at least one enormous burning fire active at any given time, simply due to the size of their org.

To navigate this, you must take the initiative in your career development and communication with managers. Understanding what you want to be optimizing for (career growth, work/life balance, new skills, etc.) and clearly communicating your desires is crucial. Be proactive in bringing information and suggestions to your manager so they can focus their limited time and energy on solving problems for you instead of guessing what you need.

You also (at least in my experience) likely have to admit that your manager or a single perfect mentor is not going to be capable of providing all you need. Building a rich network of peers and role models helps in understanding opportunities and challenges. You can also assemble a board of advisors (or a Voltron, depending on your preferred analogy) to help develop very specific skills from multiple people where no single person can provide them all.

Considering a detailed mental model of the company's landscape can aid in explicit career planning. Are there teams, projects, areas, or other that you’d like to steer your career toward? Treat your career like an enormous (hopefully very seaworthy) ship – the best way to avoid icebergs and end up where you want to be going is to notice issues early, start turning the ship, always keeping in mind the big picture of where you’re headed. Even the very best managers have limited time for your individual development – don’t outsource being the captain of your own career.