So, I think there are two models.
One is a "one junior per team" model. I endorse this for exactly the reasons you speak.
Another, as I recently saw, was a 70/30 model of juniors to seniors. You make your seniors as task delegators and put all implementation on the junior developers. This puts an "up or out" pressure and gives very little mentorship opportunities. if 70% of your engineers are under 4 years of experience, it can be a rough go.
That second model is basically the hospital model.
You have 1 veteran doctor overseeing 4 learning doctors. For example operating rooms do this, where they will have 4 operating rooms with 4 less experienced anesthesist and then 1 very experienced anesthesist who will rotate between the 4 and is on call for when shit hits the fan.
Honestly I think everyone here is missing the forest for the trees. Juniors their main purpose isn't to "ask questions", it's to turn into capable seniors.
That's also why the whole "slash our junior headcount by 3/4th" we are seeing across the industry is going to massively, massively backfire. AI / LLMs are going to hit a wall (well, they already hit it a while ago), suddenly every is scrambling for seniors but there are none because no one wanted to bear the 'burden' of training juniors to be seniors. You thought dev salaries are insane now? Wait until 4-5 years from now.
Fred Brooks proposed "surgical team" structure, where as people gain experience they "bud out" new teams - i.e. the most senior after "the surgeon" ultimately leave team to become "surgeon" of a new team
I guess Peopleware couldn't get every single thing right.
A hospital model may be a good idea. One where you have a senior programmer and many junior ones doing most tasks isn't. IMO, something closer to a real hospital team, where you have experts of different disciplines, and maybe a couple of juniors composing the team has much higher chances of success.
> something closer to a real hospital team, where you have experts of different disciplines
That is not how hospitals work. The surgery departement won't have a crack team of different disciplines to teach budding surgeons everything. They'll only have veteran surgeons to guide less-experienced surgeons.
What you will have is interdepartmental cooperation / hand-off, and you'll have multi-discipline roles like surgical oncologist.
In the same way, you won't have devops seniors training front-end juniors.
A surgery team has a surgeon an anesthesiologist, a nurse specialized on material handling overseeing the material usage in the procedure, maybe a nurse specialized on equipment handling. None of those people are junior or subordinated to the others.
In my operational team, I'm following a third model, inspired by german trade workers. You have juniors, journeymen and masters. Juniors are generally clueless and need to be told what to do, specifically. This is very much the level of "Here are 28 marks that needs bolts placed in concrete, make it so, I can explain why". Journeymen should be figuring out a plan how to solve a project and challenge it with the master to see if it fits the quality requirements of the master.
And practically, you can have one or two journeymen per master. However, these 2-3 people can in turn support 3-4 more juniors to supply useful work.
This also establishes a fairly natural growth of a person within the company. First you do standard things as told. Then you start doing projects that mostly follow a standard that has worked in the past. And then you start standardizing projects.
My first big job was the 1 junior per team; those years were extremely good for learning how to design and write high performance services. Since then, I've mostly been at the 70/30 places where I'm considered senior. Occasionally I just sit down and blast out a big software project, just to feel I am still able, but mostly I tend the garden hoping that a few of the fragile stems will survive and grow into mighty oaks.
With the subjective view on what a junior is, I think the 70-30 - or higher - model is used in any company I ever interacted with. For this evaluation I consider junior=someone with less skills than needed to do the job autonomously/require direction and supervision most time, senior=someone that can work autonomously.