You'll learn the hard way that some orgs. do exactly what you are afraid of, and some do things the smart way. If a job stresses the cool tech, the ping pong tables, competitive culture etc., be concerned. Also be concerned if they don't seem to have ANY structure, because those orgs. will bog you down in doing things that nobody else does.
If it's a clear entry level -- or open ended -- job spec, and they clearly hire at all levels or seem to be hiring mostly juniors, then you are likely on the right track.
That said, I don't think anywhere I've worked has expected those coming from bootcamps or fresh out of college to be up and running in hours. It's a known factor, and usually someone is willing to work with you if you show interest in learning.
Yes, you're quite right that it depends a lot on the organization. From my experience it seems that larger companies are better at integrating junior level people. Startups have a problem that they need people up to speed fast. That said, startups often have really great people for mentors, it's just that they might not find much time to do it.
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