Specializing is actually the "easier" path, and thus there isn't a lot of low hanging fruit anymore. There are more opportunities in the intersections of different fields (areas of mathematics).

Euler did his master’s dissertation on the philosophies of Descartes and Newton. He then joined the faculty at University of Basel in theology. I think this is ample evidence that he received a well-rounded education.

Not to mention his day job for a while as the chief cartographer in the Russian Empire.

Absolutely HARD disagree. Pythagoras, Aristotle, Pascal, Descartes, Newton, Franklin, DaVinci, (just to name a few) were all polymaths. They all left lasting impacts outside of a singular domain. It's because they were such well rounded individuals that they were so successful and capable of revolutionary discoveries and inventions. Our world is made up of models that are related with other models that are related based off of that relatedness. It's maddening. Being "well rounded" is vital.

Today that concept is watered down. A "well rounded" education is just taking a few classes that people hate and will blow off because to graduate they need to check some boxes so they can focus on doing one thing moderately well and finding their place as a cog in a machine that will abuse their ignorance. It's all mass produced conveyor belt education that manufactures young adults with little conventional wisdom. The more you lean into behaving like a part, the more you will be treated that way.

They didn't have to waste much time going to school -- and certainly not going to school with average people. That makes it a lot easier to get a good, well-rounded education -- if you are bright enough!

Euler was nothing if not diverse. Having a "liberal arts" / "great books" education from high school I have (anecdotal) first hand evidence in the impressive successes of my classmates in a WIDE variety of fields.

It's more that mathematics is solely consumed inside "mathematics for engineering 101" spread across N years.