Is there any online resource or somewhere I can see this in practice? Or any newsletter, youtube channel that discusses this in detail?
My go to sources are open source repositories where I try to understand the code bases and some PRs. But I feel overwhelmed with the resources.
One is treating your team well and developing the juniors under you, including understanding that each individual may have different needs or require a different approach.
Two is that the best theoretical technical approach is not usually the best real life approach. The number of times I've seen technically elegant code fail because of human systems is quite high. A real example... Yes, I see you used maps and spread operators to concatenate shared vs core values in a CSP file that's shared between multiple sites in a monorepo. How do you think we can maintain that between multiple teams when we don't have clear delineation of ownership? The code works elegantly, but the human processes around ownership to maintain it are absolutely garbage. You should duplicate the shared CSP for each site and task them with stripping out any unnecessary entries for their own file/site. If not, then at least we can open vulnerabilities against individual sites. But hey, telling my TL that didn't work so now we're in a shitty position.
I can't think of any substitute for experience. You can read and study what you call concepts and patterns, just like you can read about baking a cake, but you can't get experience from study. You practice, make mistakes, stretch your abilities every day, and with luck you find good mentors.
Your focus should also shift a little bit more towards helping others, thinking about where the whole team is going, etc.
But give it time. As long as you keep learning, you will get there. :)