I know this pattern from myself.
I'm doing alright as far as my career goes, not great, but okay. Which is disappointing because me and everyone around thought I'd do great, because I/they thought I was a great software developer, since I'm smart and I know my tech and my programming.
Unfortunately working as a software developer is a different story entirely, I found many times that my chase for good simple code takes time, and sometimes I overthink things and I don't test properly, and I'm also slow, and don't communicate the problem with my team because I don't work consistent hours, because my brain cannot do consistency.
Turns out I have ADHD. Possibly autism too. So I understand your feelings of I just need to be better, because it works for other right? Even tho you know that fundamentally you are right, but it works for others so why not you? I don't have a solution. But sometimes you can't just "be better" and "more consistent", I also wish I could, but maybe it's not possible.
Maybe the only way is to find where we are good and do more of that. If you have struggle finishing things hope on calls with people that are good at finishing things. Talk with them. Be proactive and be open. I also don't do this as often as I should, because I'm also ashamed.
I don't know exactly what the point was to this, but so you know others also fail, even tho they deemed smart and skilled by others.
If you recognize yourself in that post, then what you recognize is called negative self talk. The only advice I have for you is to learn to recognize how this pattern makes things worse and to learn (or be taught) how to stop that pattern. The blog post is a textbook self-flagellation and I have no doubt author returns to it to feel worse about themselves in some twisted attempt to motivate positive change.
Division of labour is THE big advantage of working with other people. So yes, focus on the bits you are good at and hand the other stuff to people who are good at that part. It's usually worth it.