C# is a great tool to have to expand on your SSIS flexibility. I found this book to be a great resource in my SSIS development. It covers a majority of the tasks that SSIS tools can't accomplish natively.
https://www.amazon.com/Extending-SSIS-NET-Scripting-Integration/dp/1484206398/ref=sr_1_1?dchild=1&keywords=.net+for+ssis&qid=1601580178&sr=8-1
I would argue that Access actually has less significance on a resume than excel.
If your interest lies more along lines of reporting then Power BI may be something worth pursuing.