This resonates with me too. Aim for T-shaped, keep an eye/ear/other limb on all the things that interest you, while dedicating some extra time to 'get good' (whatever that means to you - completing a course, solving a challenge, getting a job) in one area - probably Web dev at the moment. Then keep at it - move from T to Pi shaped, perhaps if you have the capacity/time/willpower go for Comb shaped! This of course will take time, and hopefully opportunities will arise that lead you through many learning cycles. Each 'deep dive' will also help your broader understanding across the field - some things may fit common patterns, new ideas may be applicable elsewhere.
You may find that some of your earlier expertise becomes less valuable (broken comb teeth?), and you can let it go (Delphi anyone?) or that you need to refresh it for the next challenge, where you will have the confidence of having been there already, and now have a better breadth to apply to re-learning ;)
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