That's the naiveity of software engineers. They can't see their limitations and think everything is just a technical problem.

No, work is never the core problem. Backlog of bug fixes/enhancements is rarely what determines the headcount. What matters is the business need. If the product sells and there is no/little competition, the company has very little incentive to improve their products, especially hiring people to do the work. You'd be thankful if a company does not layoff people in teams working on mature products. In fact, the opposite has been happening, for quite a while. There are so many examples out there that I don't need to name them.