If you do your day job for your employer with total dedication then you are not likely to 'need' to post public repos or get involved in slagging off different programming trends. Plus you have already heard what people have to say about your toolset and you know they know little about your domain expertise.
No word of a lie, a few years ago a 'crypto' person told me that all the code I was working exceptionally hard at was a complete waste of time. Blockchain technology would solve everything. I just had to wait. And I am still waiting!
I have a lot to show for the work I have done since that conversation with buttons I have put online getting clicked millions of times with nobody personally thanking me. It is 'silent majority' code. No idea where the 'crypto' person got, I stick to my own lane and I don't need to rubber-neck.
Although it is good to share one's work so nobody else has to reinvent the wheel, if I have a better solution and I have developed it in the context of dedication to the day job, then that software gives a commercial advantage to my employer. Even if the core of the idea is mine and that I developed it in my own time, I 'bat' for my employer, and, if it is in their interests to keep the repo private, then I will.
There is also the matter of peer review. My colleagues are too busy to spend time on my pet projects.
The 'crypto' person has one of those LinkedIn profiles where they have more than the maximum amount of connections, with all kinds of grand job titles and the rest of it. I am just a programmer and I do not need a job title. I don't even need LinkedIn and I do not spend time inventing a grander version of myself online.
For code samples I can share the code that I worked on, albeit removing any business logic that is not mine to share. In my niche, with recruiters that know me, this 'just show me the code' works fine.
What if everyone worked like me? There would be no fine repos to plunder!!! Well, there are a few pull requests I have put into public repos and the majority of the population cannot say that. Plus, if I spend two decades silently writing code, then, one day, post a repo, it is going to be good.
To be honest the code I was writing two years ago makes me cringe with shame at how naive it is, so I doubt that my efforts from before that would have been for the wider public good, even if they did fix a business problem at the time. I have sometimes had to get working code rather than beautifully refactored code, then onto the next project.