To say or call Excel as a waste of time would mean that you are looking at data science as an incredibly small silo of applications.
Data Science is not at all about the tools you use, be it R or Python or Excel. In fact, Data Science is about analyzing the data, gaining insights from it using various statistical and computer science tools and then understanding the story told by the data. Most of the time on Data Science is spent on the processing of the data itself and on understanding the existing patterns in the data.
It will be of great use to you if you begin to download data on excel, and then explore column by column the data, plot it to see any patterns and also understand the relationship between 1 variable(column) to another. Only by doing the above can you begin to grasp the way you analyze the data. Excel is also quite capable in both plotting and making linear models which by itself are a big deal. If you go through the data and learn to explore it in excel, you will have a wonderful visual intuition of what to do and what not to do when you start analyzing tools in R or Python.
I am both a post graduate in business management and now pusuing same in data science and I can tell you that if you do not know what to do with the data in Excel, you wont know what to do with it in R or Python either.
I highly recommend you to get started on your data using the concepts as taught in
Do no give up. Just barge in. I have explored more than a 100 big datasets and each dataset has its own challenges. Happy exploring.