I'll add to this from my experience in the Army because they really grok this concept. If my platoon sergeant overheard me telling a private, "you don't know X and Y," he'd dismiss that private, and he'd be demanding to know why I hadn't trained and mentored that soldier and what my plan was to fix the situation.
A good supervisor may often start by giving you a broad or vague objective, "I'd like you to understand X and Y," but if you don't get there, your supervisor's responsibility is to figure out why and develop a plan of action.
> ... that company has the responsibility to give you focus and training on the requisites.
There are specific business reasons behind this: they need to maintain a team of people who are delivering enough value that the company can fulfill promises it makes to shareholders.
> The blame is never on the IC, unless they're not trying.
In the private sector, this is true, the IC won't get blamed. They'll get fired, and the supervisor will get blamed, but that doesn't help you much.
To make it work, the junior IC needs to build confidence in his managers that he's able to produce at the team's level. And you can take action, probably as simply as saying, "let's make some kind of agreement here that has specific deliverables."
To work out a plan, it helps to consider what they're looking for with stuff like "you should know how to X by now."
Contrary to popular belief, technical work is not a meritocracy, it's a mediocracy. If you're much better than everyone else, you can't share your work, and if you're far behind, you're not able to contribute. Having a bunch of people on the same "level" enables throwing more bodies at a problem.
> Never feel ashamed for not knowing something...
I'll add another thing to not be ashamed about, which is not being good enough to stay on a team. Even if it's theoretically possible for anyone to learn anything, time and expertise in teaching are scarce, so "train person A" has to be compared to "replace with person B."
Another military anecdote: I signed up as a cavalry scout, and learned to my dismay that I have no sense of direction. I managed to get by and finish my enlistment, but it was enough of an impediment that I'd never make rank.
It may be fucking soul-crushing, but it's not shameful if you give it your best. Work out a plan to get yourself to where you need to be, but account for the fact that failure is always an option. Prepare to take ownership of it, to candidly reassess your strengths and weakness and be ready to drive on. And be glad you didn't sign up for a goddamned five year enlistment.