MacOS Big Sur 11.0.1
why can I not download this on my computer? I have an IMac (Mid 2011) its currently running OS X Yosimite
iMac Line (2012 and Later)
Very simple, the computer is WAY too old and does not have the hardware to go beyond 10.13.6, Big Sur. If you have a need to go beyond Big Sur 10.13.6 then it is time for you to get a newer Mac. It is that simple and in-case you are wondering, no there are no work arounds.