Intelligence is mostly down to genes. You can invest as much effort as you want but you can no more turn yourself into a genius at will than you could decide to grow into a giant by choice. Hierarchies based on intelligence are roughly as fair as hierarchies based on looks, athleticism or caste. Beating yourself up because others are smarter or learn easier is the same as beating yourself up for not being born into a wealthy family or into a more attractive body. It's not your fault our society is too stupid to recognize this. Nor that it has failed to take responsibility for its people's genetic makeup. Maybe do an IQ test if you are still uncertain where you are at on the thinking men's ladder and then just accept what you have to work with. If you have some kind of unrealistic intellectual ambitions, pride or hopes in your heart and they are torturing you from the inside, then it's simply time to put these parts of you down by force.
You probably are at least 110-115 IQ if you got a degree. But if you really read lots of non-fiction literature in your free time, you might be much higher. Your perspective on your own intellectual capabilities might be skewed because you are comparing yourself with people at the very top. Maybe because they are your peers. But you yourself might only be slightly below them in terms of intelligence. Think imposter syndrome is the official term for that.
When it comes to your life in general, I would guess that, considering you haven't found what you are looking for yet, it's not hidden in the places you have been looking in till now. If it does exist at all.
From personal experience, I made a lot of progress after leaving my comfort zone. Hiring a prostitute, fixing my relationship with my mom after opening up to her about all the pain and misery in my heart. Going to speed dating events (was hell, would not recommend), just generally doing the things I knew I would normally never do. Many attempts did not go well, but I learned that there is a difference between the pain I feel from the regrets I carry over all the things I didn't do and never gave a try and the pain I feel from having tried something and having seen it fail. By now I'm certain I prefer the latter.
What helped me make small leaps forward was the support of other people (e.g. social workers, therapist, my mom) and my belief that AI is probably going to kill us or otherwise ruin our lives as early as 5-10 years from now. With that in mind, I finally got motivated to seriously try getting my life in order. And more comfortable with taking risks since the outcomes don't feel like they matter as much if we all are going to die soon anyways.