Mojave blank screen of death

I have a 2013 iMac and after an attemp to install Mojave I got an unusable computer. It gave me a blank screen. Absolutely nothing. So what is next for our computers that are running just fine on Sierra? No more updates to keep our computer safe? No more support? I guess it is time to nix the iMac and get a windows pc again. I would not recommend Mac to anybody now. My husband has a windows machine with 10 on it and it works like a dream. But with mine ... Apple keeps on trying to update my machine with the unusable "Mojave".. Apple has failed a lot of Mac users with this Apple platform. Not a smart decision Apple. How come you could not make a different format for all the older (still working great) iMacs in circulation,? because Apple wants to chip our HD so they can bank on repairs. SHAME!!!