Saying ML is "just linear algebra and calculus" is a gross simplification.

As a dev, you can pick up some popular ML frameworks and learn the basics relatively quickly. The difficulty in this field comes from the amount of theoretical knowledge you need to interpret your results.

All these data science bootcamps/learn quick schemes are like teaching a blind person to drive a racecar. He can work the pedals and the steering wheel - but has no idea where he's going.