I love my current job as a junior developer. However, I work with two (quite brilliant) seniors who pretty much don’t let me in on things I can learn from them. At this point in my career, is it important to have mentors who will help me further my skills? Will I do just fine gaining knowledge via the internet and other resources or should I start looking for a job elsewhere?
Working with senior developers will definitely help your career and, in my opinion, is critical to becoming a better developer. Before looking for a job elsewhere, I would try to be more assertive and insist on being included in projects/implementations/fixes that the senior developers are working on. Also, do they review your PRs or do any code review? If not, I would suggest you bring that up, that's pretty important.
You can always use the internet and other resources to expand your knowledge but I have found the mentorship/help from senior developers invaluable.