"We don't need juniors anymore since we have AI." What awaits at the end of that road? Ruby creator Yukihiro Matsumoto's warning is not mere nostalgia. It is a visceral concern about a future where technical knowledge transfer has ceased, leaving behind nothing but "scorched earth."

What Is the "Juniors Are Unnecessary" Argument?

With generative AI evolving at a breathtaking pace, code generation tools have become remarkably accurate. This has fueled an active debate in the IT industry: "We don't need junior engineers anymore."

Videos of AI creating Tetris in seconds go viral on social media, leading some to declare, "Engineers are obsolete." According to Stack Overflow's survey, AI coding tool usage reached 84% among developers by 2025.

This trend is clearly affecting young engineers' employment. A Stanford Digital Economy Study found that employment for software developers aged 22-25 declined nearly 20% from its late 2022 peak by July 2025.

Yukihiro Matsumoto's Deep Concern

Against this backdrop, Yukihiro Matsumoto, known as "Matz," the creator of Ruby who has been at the forefront of programming for over 30 years, has voiced clear concerns.

What awaits after dismissing juniors as "unnecessary" is a "scorched earth" where technical knowledge transfer has ceased, Matz warns.

According to Matz, AI-powered "vibe coding" is "like a gacha game," where you never know what you'll get. While AI can reproduce existing simple programs with nearly 100% success, trying to create something new fails "99% of the time" in his experience.

In other words, AI is merely a "capability amplifier" for people who can already program. Without humans who can guide AI, fix its mistakes, and design new things, work simply cannot get done.

Without Juniors, There Will Be No Future Seniors

The core of Matz's concern is the "discontinuity" in talent development.

Junior engineers grow by handling small tasks and gaining practical experience. Through this process, they understand system architecture and learn why things were designed certain ways.

But if AI replaces junior-level work, the opportunities for young engineers to grow will disappear entirely. And if juniors don't develop, there will be no senior engineers in the future.

AWS CEO Matt Garman has also pointed out that replacing junior developers with AI is "one of the dumbest things" companies can do. Young people not only grow into future seniors but already know how to work effectively with AI coding tools.

Japan's Unique IT Talent Challenges

This problem is particularly acute for Japan.

According to the Ministry of Economy, Trade and Industry's estimates, Japan could face a shortage of up to 790,000 IT professionals by 2030. Additionally, Japanese IT workers tend to have lower skill levels in international comparisons, while engineers in the US and India average skill levels above 4, Japan's average remains in the lower 3s.

Furthermore, Japan's IT industry's unique multi-layered subcontracting structure compounds the problem. Companies handling downstream processes (programming, testing) are doing exactly the work most susceptible to AI replacement.

The "2025 Cliff" problem has also materialized. While companies struggle with legacy system maintenance and fall behind in adopting new technologies, the engineers capable of handling these challenges are retiring.

Four Skills Needed in the AI Era

Matz proposes four skills that young engineers should develop to survive in the AI era:

1. Ability to Guide AI The power to detect and correct AI mistakes. AI might output 4-space indentation even when you specify 2 spaces. Humans who can catch such errors and provide appropriate guidance are essential.

2. Programming Fundamentals AI excels at reproducing existing things but struggles with creating new ones. Without design and programming skills, you cannot effectively utilize AI in the first place.

3. Problem Discovery Ability Deciding what to build is a human job. The ability to determine "what" to ask AI to do becomes crucial.

4. Communication Skills Software development is teamwork. In an era of human-AI collaboration, the value of human-to-human communication increases.

Sustainability of OSS Communities

Matz also addressed the sustainability of Open Source Software (OSS) communities.

OSS that underpins modern software development, such as Ruby, Linux, and MySQL, is maintained through community contributions. However, as projects grow larger, maintenance costs also increase.

"Unless large companies say 'We benefit from Ruby, so let's give back,' long-term maintenance becomes difficult," Matz notes.

Not just funding, but human contributions matter too. If junior engineer development stagnates, fewer people will be able to contribute to OSS, threatening the entire ecosystem's sustainability.

A Global Discussion

This issue is being debated worldwide, not just in Japan.

David Heinemeier Hansson, creator of Ruby on Rails, argues that current AI tools "still can't match most junior programmers." AI sometimes produces correct code, but it's like a "flickering light bulb", unreliable.

Meanwhile, Anthropic CEO Dario Amodei suggests that within 1-5 years, half of entry-level white-collar jobs could disappear. CEOs of Google and Microsoft have also stated that AI now handles 20-30% of coding work.

Amid this mix of optimism and pessimism, one thing is certain: change is happening.

How Should Japan Respond?

How should Japan address these challenges?

First, don't stop developing young engineers. Reducing junior hiring for short-term cost savings leads to long-term technical hollowing out.

Second, view AI not as a "threat" but as a "tool," exploring new development styles where humans and AI collaborate. Let AI handle what it does well while humans focus on design and judgment.

Third, foster a culture of continuous learning. In an era of rapid technological evolution, skills learned once quickly become obsolete. Both organizations and individuals must maintain a learning mindset.

What About Your Country?

In Japan, AI evolution and IT talent shortages are progressing simultaneously, highlighting the challenge of developing young engineers.

What's the employment situation for junior developers in your country? How widely have AI tools penetrated your development workplace? What discussions are happening about training young engineers?

Please share your country's situation and your thoughts!

References