Feels crazy how fast these past 5-10 years have flown by. In our clinic we have ~30 iMacs, most of them 2011 models. ~3 years ago or so I replaced all the disk drives inside with SSDs. They’re 7 years old now and run just as fast as when they were brand new.
I still have to turn down the monthly call from Apple Business reps about upgrading or leasing new machines.
You should mention to them that their current lineup is horrible and they need to get with it, or be honest with Mac clients and just kill the whole line.