It's all about the Nordgens. Those being sold by real managers are mostly useless second-hands.
It's the teen-aged Nordgens that come with special abilities that are the most useful players. And yes, there are seasons where the market is flooded by them, so much so that they go unsold, and then there are other seasons when there are exactly zero five-star Nordgens for sale the entire season.

It has been a problem that should be easily fixable, yet Nordeus refused to do it.