Au contraire, there's a difference between social skills and introversion.

You can be introverted and have strong social skills. In fact, if you want to be successful, you will need strong social skills. Development is one of the few areas in which this is not the case, although the people who move up will have the strongest social skills.

Some will view it as playing politics, being manipulative, what have you. But ultimately these aren't personality traits, they're skills.

It's possible to be an extrovert with bad social skills, i.e. you're obnoxious. Or an introvert with fantastic social skills, i.e. you're the next CTO. Some, maybe even most, introverts don't know this. So they don't develop their skills and wonder why they don't succeed.

All to say, the recruiter is 100% right. How CAN you be 40 with such poor social skills? Well, you're an introvert and everyone has told you your whole life that's not for you. So you purposefully ignore those skills.

As you alluded to, it's also easy to forgo chasing these skills when we can make decent money just solving puzzles while only requiring the most basic of emotional intelligence.