Are you capable of maintaining a fork no matter the language or level of complexity? Are you going to maintain your own fork of Chromium? WebKit? MySQL?
But if you don’t have the time or energy, you don’t have the capability.
I might as well say I have the capability of flying my own private plane if I had the money to buy the plane and the time to learn how to fly it.
Obviously yes, the more complex the more difficult. And if it's a technology you don't have experience with it's going to be extremely difficult to impossible. But that's not what I'm talking about.
I'll give a clearer example taken from my actual job:
At my job, we needed to use a NodeJS library to accomplish something. We found one, but it eventually fell out of maintenance. We discovered a bug that was blocking us from continuing to use it, so we had the choice: fork it or find an alternative. We chose to find an alternative because even though we had the technical capability and understanding to fork the library and fix the bug, we realized that would be one more piece of infrastructure that would take time and energy from our team which are a finite supply.
It's more equivalent of an airline pilot saying "I wish I had more time and energy to fly a plane for fun, and not just for work." The ability is there, just not the bandwidth.
But if you don’t have the time or energy, you don’t have the capability.
I might as well say I have the capability of flying my own private plane if I had the money to buy the plane and the time to learn how to fly it.