I think you are correct. Your problem isn’t that you don’t have enough friends. The problem may be that you have set a standard for “enough” that isn’t realistic. You say you have a few friends. You say that you keep meeting people and that you are involved in many activities. That suggests to me that you in fact know a lot of people who know who you are but you don’t think you have enough close friends in your inner circle.
We live in a time when people have hundreds of “friends” on social media and where stories in movies and TV shows seem to indicate that life should be populated by many, many people being involved in our lives. It may be some comfort to you to know that research doesn’t support it.
You are in your 50s. Most people your age have 3 – 5 really good friends in addition to a few extended family members who are important in their lives. Think of types of relationships as being like an archery target. The middle bullseye is you. The next circle is that 3 – 5 good friends and family. The next circle out is for acquaintances and work people — people you see regularly who know you a bit but they aren’t people you would confide in. Beyond that is a circle of people you recognize from your community or church, etc., but don’t relate to other than a smile of recognition or a wave. The next circle is populated by strangers.
It is also true that when we reach adulthood, it is harder to make friends than it is for young people. Adults often already have enough friends and family members to keep track of. Friendships take time to develop and maintain. Often people’s lives are so packed with work, family obligations and personal stresses that there simply isn’t time to take in a new friend, even if they would very much like to.
I think you should focus on maintaining the friends you have and getting other social needs met by continuing to engage in activities and work that you enjoy. Perhaps some of those relationships will evolve naturally. But I do want you to know that having a few good, good friends puts you well within what is normal.
I wish you well.