Why is my 2018 tax return 121 pages long?

Because it not only contains your completed tax return forms and schedules, it also contains all the worksheets and informational pages for your tax returns, both federal and state.

Every year, after you file and before the end of the Online season the end of October, log in and  save a PDF of the return as filed.  Once the returns have been archived the only option you will have is the PDF with all the worksheets included.