This sort of boils down to two separate issues.
Issue 1: what is the minimum length of time you can stay at a job, without looking like a job-hopper on your resume.
For software developers in the current market, I think many would say 1 year is the minimum. Note also that job-hopping is a pattern of short stays, so if you have only a single less-than-1-year stay on your resume, it won't necessarily signal "job-hopper" -- that one short job was an exception, and you can explain it.
That said, the longer you can stay somewhere, the better it looks.
Issue 2: how can you become less uncomfortable working in an environment where you don't have guidance from those more experienced.
You will need to do this until you have stayed there long enough -- whatever length you decide will make you not look like a job-hopper.
Part of this is just managing your own expectations. You and your fellow juniors are going to be writing not-the-best code, making rookie mistakes -- it's unavoidable. If management knows there are only juniors left and isn't hiring seniors (right now), then you have to accept that, in some sense, management is okay with this (right now). So don't worry so much about it.
I am writing stuff to a "it seem to work" standard in Angular, a framework I have never used.
Sadly -- and I say this as a senior developer -- a lot of the time, "it seems to work" is more or less the highest standard you can reasonably hope for.
And that standard, honestly, doesn't come from exquisitely-written code and exhaustive knowledge of the technology in use. It comes from understanding the problem correctly and having sufficient tests.
If the test suite is exhaustive enough, and reflects what's actually needed, the code can be absolute rubbish, and the thing will still work. Which is, at the end of the day, what the business needs to happen.
Having said that, the more you know about the tools you use, the easier it is to reach that point. But always remember that even seniors use StackOverflow to get solutions to their problems. (Constantly!)