That’s scarcity mindset and it decimates your potential for negotiation. If you really truly believe you are a commodity and have nothing at all to offer compared to any other candidate, it’s worth either learning something new to get out of that commodity category and/or look at your experience + knowledge outside your core specialty and market that better.
It sounds cliché but there is nobody like you. We all have unique experiences (life + professional), hobbies, knowledge no one else has or at least not in that particular combination. That’s your « unfair advantage » as some call it and you absolutely can use it to your advantage.
The choice is yours.
I have things like Haskell, Lean and Prolog on my CV - definitely not things that everyone else has had experience with. Recruiters/HMs generally aren't interested in these kinds of things. Oh but you have worked with Kafka before? Now that puts you ahead, even though so many others have.
The one time I tried to negotiate for a director position they responded along the lines of "Oh we're sorry if we implied that this was a negotiation. You can accept or decline the offer by the end of the week."
LOL we might have applied at the same company. That's almost word for word what I've heard in the past: "Oh, sorry, we must have been unclear: the offer is not negotiable." I said NO and they said "OK, thanks for applying."
I’m an average software engineer and I can’t remember a time where I took a job I didn’t negotiate the salary on. Companies that refused to negotiate were the last offers I’d consider and I end up not taking their offers. I was often better paid than my peers. And my professional accomplishments are far from exceptional, I’ve never worked for any companies you’d know, I have gaps in my CV.