Upgrading OS NOT to high Sierra

Hello,

I run a complex fine art reproduction business and need to upgrade my one of my iMacs (OS Yosemite) to a more current version. If I install High Sierra, many of my programs and print drivers for digital printing do not support this sudden change. I did upgrade to High Sierra and it was un-usable with our complex variety of print drivers, colour profiles and image manipulation software, and had to revert back to OS 10.10. Why can I not find a lower version to install and slowly upgrade my OS. This has been an issue ever since I started to work with Mac computers (OS 6). In the old days, one just needed to find a dvd, but now that the OS is online, I cannot get anything but the highest version online. This issue has cause soooo many problems over the years and Apple just doesn't offer any help (older versions available). All I want to do is upgrade between OS Yosemite and High Sierra. I would pay for access. I have been a power user since the beginning of OS 6, why, oh why is there not a solution for this? I understand that if I had downloaded a previous version in my account, I could access the right OS, why would I not have access to all the OS versions. Is the only solution to my problem to wipe my drive and reload a huge assortment of programs, fonts, drivers, profiles, email archives, bookmarks, calibrations, etc?