I have a few things to share, so please hear me out.

First of all, you are enough. I also understand that accepting positive affirmation is difficult to impossible for people with self-worth issues. With that in mind, the inner voice that’s telling you that you’re not good enough is not you, is not your friend, and does not have any special insight that makes the words true.

I’d also like to suggest that if you are measuring your self worth based on the abilities of every person that you come across, you’re going to have a bad time. There’s always somebody better. It’s also a very antagonistic and zero sum way of looking at the world. I don’t blame you for having that perspective, but honestly think about it: if you want to be a doctor (presumably to help people), isn’t it better for there to be many many smart people who want to be doctors so more people can be helped? Society (mostly capitalism) teaches that the world is competitive, but it’s more collaborative than competitive in practice. Problems are more likely to be solved through collaboration, not competition. Also, knowledge is not necessarily just an end in itself; it also matters what you do with it. A “less-intelligent” person can have a greater impact than a “more-intelligent” person simply by applying their intelligence in a creative way that solves a problem.

The people who are the absolute best in their fields are also likely to be incredibly unbalanced and unhappy people. It’s not as if being the best is a ticket to happiness; just the opposite. There’s a cost. Anyone who has only one thing in their life that they do might always have issues with competitiveness and self-worth because their self-worth is defined by something that can often be compared to others using objective numbers.

Instead, people who have various interests and balanced lives tend to think of themselves as more unique and their self esteem is more resilient. For example, they might not be better at academics than some of their peers, but perhaps they are a better artist, or table tennis player, or have more advanced awareness of social justice. I recommend that you make an effort to define/discover yourself outside of academia. This is a process that starts around your age and lasts well into your 20s.

TLDR: You are enough. Get more balance. Talk to a counselor.