Can a lone programmer become a mid or senior level programmer without a mentor? [duplicate]

Question

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• Improving without mentor [closed] 9 answers

Question:
Can a mere entry level programmer become a mid or senior level programmer working in a company as the only programmer without a mentor?

Background:
I was hired as an entry level programmer for a mid size company that does not do programming except for internally. I am regarded as a genius inside the company with a decent salary but after 2 years I decided I wanted to move to an actual software company. The interview processes have been extremely demoralizing because even though I have wrote intra-company enterprise applications these interviews have made me aware of how little I actually know.