Upgrade iOS

I purchased Turbo Tax 2020, only to find out I can't upgrade High Sierra to Mohave because my

hardware is a year too old. Is there any way to upgrade my hardware to run a newer iOS version?

All I see are spec requirements as answers to the many times this question has been asked, but

not one answer from Apple says I have to buy a new computer. Do I really have to trash my

whole system to upgrade THEIR software?