Slow iMac
My and my son's brand new iMacs, out of the box, are slower than either our iPhone 7s or our ancient MacBooks. After hours of frustration, compounded by working and schooling remotely, for months, we went around and around, hours on the phone with Apple Support, with safe boots, zapping pram and activity monitoring and scrupulously closing browser tabs, nothing. I think now that the real issue is the hard drive, which is frankly obsolete, and which I didn't even check because since 1986, I have been a devoted and trusting Apple user.
Can we solve our issues by purchasing inexpensive SSDs as our boot and application drives, keeping files on the iMac hard drive and the cloud?
iMac 21.5″, macOS 10.15