What has happened is that the "old generation" of programmers is dying out / retiring. And they aren't passing on their knowledge to the new generation. The "old generation" of programmers were high-math, abstract algebra and more, while "new generation" programmers just never bothered to learn this stuff.
There may be some survivorship bias here. Even in the 1990s, business-grade programmers (the ones who, quite frankly, aren't inclined to learn difficult subjects) either went into management or did something else, although the timeframe and ageism are more aggressive these days due to the infantilization and humiliation (e.g., Agile Scrum) that engineers face today.
Research-grade programmers were the minority, even then, although this problem is a lot worse today due to the near nonexistence of R&D jobs.
There may be some survivorship bias here. Even in the 1990s, business-grade programmers (the ones who, quite frankly, aren't inclined to learn difficult subjects) either went into management or did something else, although the timeframe and ageism are more aggressive these days due to the infantilization and humiliation (e.g., Agile Scrum) that engineers face today.
Research-grade programmers were the minority, even then, although this problem is a lot worse today due to the near nonexistence of R&D jobs.