There is a huge pool of exceptional junior engineers

When I hire juniors, I try to give them problems that I know they likely won't be able to solve in the interview because I want to see how they think about things. The problem has become that a lot of kids coming out of college have done little more than memorize Leetcode problems and outsourced classwork to AI. I've also seen less and less passion for the career as the years go by (ie. less computer nerds).

Unless the company is doing something that requires almost no special domain knowledge, it's almost inevitable that it's going to take a good while for them to on-board. For us, it usually takes about year to get them to the point that they can contribute without some form of handholding. However, that also mostly holds true for seniors coming to us from other industries.

I noticed I had an immediate bias against candidates that showed up to interviews using Windows (except for one person who was in WSL and seemed very comfortable in bash), or, not having their SSH key set up for cloning the github repo we used for our interview, or fumbling back and forth with their mouse between vscode and the browser, not using all their screen real estate, or not knowing even the most basic of keyboard shortcuts (I nearly cut an interview short once when I saw someone right click copy right click paste in vscode but I wanted to give them a fair shake so gritted my teeth and went through with the rest of the interview. They did poorly.). I never used it as a for/against factor but for me lack of interest in computers, and a lack of familiarity with the tools of our trade, is a red flag.

On the flip side, immediate green flags for me were: using linux, using keyboard shortcuts to manipulate windows / within the IDE, using an IDE other than vscode (vim/nvim or emacs are huge green flags), having custom scripts, having custom themes, or, the biggest one, self-hosting some applications. And Lo, these candidates also seem to perform the best in my experience.