the whining of a young person

Mid thirties.

What this sounds like to me, to be quite honest and blunt, is about a person who is only doing what developers have always done for decades.

You are correct: developers have indeed, pushed buggy code in languages they don’t understand, for decades. And then proceeded to have noisy, disruptive opinions about it.

and many new startups

This is a blue chip org

But if this guy has been there a long time

About a year

He’s probably got kids interrupting him

He lives alone

And also, speaking from the same age and experience level, I can tell you that things like prostate cancer and colonoscopies can have a very real effect on your ability to keep details of dev conversations in your head with the same effectiveness and accuracy that you had in your 20s and 30s.

Do you also angrily demand that everyone “stops making it complicated” and repeat things that were covered at length in a previous meeting you allegedly attended? If so, I have a job for you.

Have you even considered making an effort to befriend this guy?

Yes, several times, and he’s just as awful outside of work as in it. Worse, actually.

You’re acting like an entitled prick

I already listed that I can tolerate slowness, stubbornness or disengagement individually. I don’t mind someone being slow if they aren’t a highly volatile, temper tantrum throwing manchild. I can even handle temper throwing manchildren if they are actually capable of shipping working code.

He can’t though. Something about that story clearly resonates with you.