The display is an example. I have bought an iMac in the past, I regretted it because if anything goes wrong it's a non-standard form factor and it's expensive to fix.
I would happily pay more money for an ATX case with standard components and a separate display. It saves money in the long term because you can do repairs yourself and buy standard replacement parts. This also means if something goes wrong my computer can be repaired on the same day.
If you want the iMac, or you want MacOS, then go ahead and buy it. Just remember to budget for the cost of repairs and the impossibility of upgrades later on.
