You have to keep in mind, the less capable you are with computers, the more computer you need. You might get by just fine on 8 GB, but Grandma, with her three anti-malware suites, two active malware infections, corporate spyware, and fake version of Google Chrome which reports all browsing usage to the Neilsen corporation, is going to slow to a crawl, at best, even on 16gb. Normal people computers are different than yours or mine.

How does grandma install all of that on macOS?

Yes, we are vastly superior with our enormous brains.