Disagree slightly with this- pronouncing the tones individually and getting to the point where you can be understood isn't too hard (well still hard), but combining them when speaking more quickly is more challenging, especially if you want it to flow nicely, and adding emphasis while maintaining the tones. Not that it's mandatory if you just want to understand/be understood, it depends on one's goals.
It's a common misconception that it's enough just to learn the tones and move on and it's very hard to find teachers who are able to help with more advanced pronunciation
