Some of those ideas may seem trivial and obvious, but it's better to make them explicit.
You can get answers to any of your questions much faster than doing a proper research on your own. This benefit alone can save you several weeks of your efforts. I personally have sometimes shaved off months of trial and errors just by asking right questions in the right communities. How do you think 10x engineers are made?
Shared Goals and Mindset
Our goal is to help each other learn, grow and succeed.
Knowing that is helpful to feel secure and get the honest perspective on your ideas and actions.
Having people with similar mindset next to you may be a valuable resource and a basis for trust. You can find an employee, and employer or a business partner who will share some of your values by default.
You can be sure that people around you have received the same basic training as you. You can also impact what kind of training they get!
This network effect is one of the most beneficial things in MBA studies and startup accelerators alumni networks. Here is one example.
Enhanced Accountability and Verification
Having a group of people who want to get objective results around you is priceless, as you will hold yourself accountable and will hit your commitments more often.
Also, you can relate yourself to those people and their experience and get the "if they can do this, than I can do this too" effect. There were countless episodes in our experience where we uncovered some crucial differences in the approaches people take or unique context factors which led to eventual success/failures, even though people were doing the same things.
People Do Grow
One of the long term effects is that people in the community do grow, learn diverse things and succeed in the industry and life. Everyone accumulate their unique experience. We all can learn from each others success and failure stories, work anecdotes and unique blend of knowledge.
In several years, some people will become CTOs, Founders, Engineering Managers and Masters of their craft. Having an access to people who can make great stuff is an invaluable resource, as well as having direct access to the leadership knowledge.
The Benefits of Number
As a community, we can get much easier access to the information, contacts and resources all members have. For example, when there is a substantial number of members, we can negotiate discounts for services, books and courses. Also, we can help bootstrapping the valuable ideas and projects.
One additional effect is that with a powerful community comes the power of the brand. This may be beneficial if you have not yet established your personal brand or you do not have a vast social network you can draw insights on your own.
The world around us is constantly changes. Some practices die out, some practices becomes standards of the industry. Some things remain truly foundational.
Having people all over the world in different companies and various business domains will help maintain a high level of awareness of industry trends without the need to filter that information on your own. Also, it's a great source of "hidden gem" opportunities you won't find in the wild.
At the end of the day, you can learn on other people experience without making the same mistakes. You can better understand the difference in context and suitability of different tools without making expensive experiments on your own.