> when I was a new grad I started on the codebase more or less right away

I did as well, but...

> Didn't even have code reviews back then.

Not so much this one.

> If you have to train them, then it seems the coding part should be cheaper then the algo part.

I do actually agree. But there tends to be other aspects of the job outside of just code and algorithms. Prior work experience is a shining star compared to a 22 year old in any field. I see my coworkers more than my family. Someone that has a full understanding of everything that goes along with that has a head start across the board. Someone changing careers in their late 20's also tends to put a hell of a lot more into improving themselves than just the basic progress-of-life learning. I just think it evens out as long as you're consciously hiring people for the right role.

I don't know, we pay people to do a job. Sure some coworkers become friends, but most don't. As long as people are somewhat easy to get along with I don't think we should focus too much on other stuff.

I wasn't implying that they should become friends. I meant that the working world doesn't tolerate the "I'm definitely right" mentality that comes with God's greatest gift, the 22 year old college grad. I'm joking about that last part, but there is a certain tact that only comes through time. A 25 year old is much more willing to say "I'm wrong, and I have no idea what I'm doing" than a 22 year old. This alone is a huge productivity boost. Both technical skills and soft skills can be learned, and I'd argue both are equally challenging.

I think you are right and it is much more pleasant to work in a team with people who doesn't have to be right all the time. At least I think so :-)