As an undergrad, I was doing all those easy ML tutorials and took an undergrad level ML course. I thought I would be useful in actual practice, but knowing the whats/hows of neural nets/clustering/etc. is not enough. Feature engineering/math is the most difficult part. In a corporate setting, if it was a straight forward solution, you wouldn't be doing that work because the solution would be trivial and already implemented.
As an engineer with only a bachelors on a ML team full of PhDs there is a definite difference in skill. I've been reduced to a monkey (a content one) that works on the data pipeline. Learning to deal with real world ML problems would take me years of work that I am not sure I would be willing to do, especially when the pay increases per effort expended learning ML is much lower than with regular software/distributed systems/etc..
On the interest part, you're right that I would never have tried to learn ML if I had known the amount of work that is required to actually be good or if I tried learning the math first. That's the real world though. The useful ML engineers did learn the math. The efficient way to learn ML is to learn the math/statistics first.