When Japanese Prime Minister Shinzo Abe announced his pending resignation last week for health reasons, he had been in office nearly eight years, the longest such stint in Japanese history. But even that wasn't long enough to fulfill the potential of his premiership. His successors would be wise to appreciate why.

Abe will be remembered for many changes. His three-pronged "Abenomics" program of loose monetary policy, fiscal stimulus and structural reforms scored some initial successes — boosting growth, stocks and employment. His government brought an unprecedented number of women into the workplace and immigrants into the country.

Most dramatically, Abe bolstered Japan's geopolitical standing by strengthening its military and pushing through free trade deals.

Yet whoever follows Abe will confront challenges. Growth, wages and inflation never really picked up sustainably; now, after pandemic-related lockdowns, the economy has shrunk to the size it was before Abe took charge. The list of unfinished tasks is long. Regulations that stifle entrepreneurship and innovation still need to be slashed. A seniority-based employment system that impedes mobility and wage growth needs to be shaken up. Too many Japanese remain trapped in irregular work with few benefits and career prospects.

Even in areas where Abe made a good start, much work remains. The precariousness of most women's jobs has been revealed; more needs to be done to address gender pay gaps. Broader changes will be required if Japan is to attract the number and quality of immigrants the country needs.

Abe can claim his greatest achievements in the international arena, where he has built Japan into a forceful advocate for the liberal, rules-based global order. He has also been instrumental in developing a regional response to China's rise. Yet here, too, more could've been accomplished had Abe avoided unnecessary distractions, such as a futile trade spat with South Korea and a long, controversial campaign to revise Article 9 of the Japanese Constitution — the so-called peace clause.

Such heedless efforts may help explain why Abe backed off from pushing more drastic economic reforms earlier on, when his mandate was at its strongest. If Japan is to meet its steep demographic, financial and strategic challenges, his successors cannot afford to make the same mistake.

FROM AN EDITORIAL ON Bloomberg Opinion