The only relationship which is indispensable is with your Innermost Being.
You can absolutely progress without external groups. Groups and schools are very helpful in very necessary for the proliferation of the teachings. Nevertheless, there are many who, despite having an external group, never learn to search within.
The one who is able to work on their inner work without external groups develops a robust inner strength.
That being said, the condition of being a loner is also something you must confront. There is an introverted characteristic to great sages, yet, they were not introverted in a mechanical or unconscious way of being "awkward" or "not liking people", etc.