I'm the tech lead of a sizable team, and what you describe, leaving junior engineers behind, would be a sign of failure on me.
Large software systems are complex, and there is too much detail for any one person to dive deep into everything, so in my opinion, you discuss overall architecture with the team, but critically, you explain _why_ you are proposing a certain approach, because more junior people don't have this context. Then, you ask the other folks to help you go deep into investigations on whether your architecture is compatible with the details.
If as a TL, you are not teaching and nurturing your young 'uns, you're doing a bad job.
What if your young 'uns just do not... participate?
I am in a position where I am doing TL-level decisions, and try quite hard to demo, discuss, share the details and rationale. I write design proposals, documentation, do demo sessions, etc
But the information is just not flowing, and I notice how little the juniors participate in anything. And I don't exactly know what to put my finger on. It's probably some soft-skill I'm lacking, and that I do not know how to improve
But a part of me still feels that that perhaps the young 'uns are just... too fresh. Or that the approach is just too optimistic
This is where people management comes into play. It's really difficult to identify why someone isn't participating, until you get to know their work and personality. I have regular meetings with all the engineers to discuss their work, progress, what is holding them back, expectations for career, growth, stuff like that. It's impossible to completely separate tech leadership from people leadership.
In my experience, usually, lack of participation comes from a lack of self confidence in one's understanding of software development, and usually, finding something small and delegating ownership to a junior engineer, with some oversight, gets them to participate more. You have to let go of the notion of having something done perfectly and allow them to make their own mistakes, but don't let them make huge ones. This is the most common case. There are also people who don't care (can't do much here), or aren't very good technically.
Large software systems are complex, and there is too much detail for any one person to dive deep into everything, so in my opinion, you discuss overall architecture with the team, but critically, you explain _why_ you are proposing a certain approach, because more junior people don't have this context. Then, you ask the other folks to help you go deep into investigations on whether your architecture is compatible with the details.
If as a TL, you are not teaching and nurturing your young 'uns, you're doing a bad job.