short answer: No. they are not important skills, and they will not help you get a job as developer.
long answer:
Generally a halfway sane company expect their developer to learn to work with new things, because they can not expect anyone to know everything. So whether you do or do not know your way around Excel is not an issue. It is far more important that you know how to program neatly, and pick up new skills all the time.
On the other hand there probably are some businesses that specifically work a lot with Excel. In interviews with those companies you'll have a slight advantage over the other applicants. But they will probably just as easily choose someone else because they can always teach somebody the ins and outs of Excel.
Note: I hope you define skills with Excel as developing with or for Excel, not using a spreadsheet.