It's the lowest option, you can upgrade to 32GB or 64GB on the 27-inch version.
You can upgrade the drive to an 2TB SSD, or a 3TB fusion drive.
If you only buy an iMac for the basic things like browsing, emailing and watching youtube, 8GB is more than enough, especially on macOS.
I don't get the hate for having a lower-budget option.
i don't think the ram is as much of an issue as the drive speed these days. it's not "lower budget", it's just a "low budget" option, but it damages the brand experience to have such a poor performing option available (speaking of drive speed specifically).
The day they take out the entry-level option people on here will be complaining about how they just want a decent desktop for their parents to browse on, or for them to upgrade themselves. I have 8gb and keep big music projects in Ableton open, a ton of Chrome tabs and several Electron apps open all the time, and I haven't had any issues yet.
I find interesting that you say "especially on macOS", personally I feel that macOS has the highest memory requirements of the major OSs, but I haven't used macOS in a while, so that may have changed...
If you only buy an iMac for the basic things like browsing, emailing and watching youtube, 8GB is more than enough, especially on macOS. I don't get the hate for having a lower-budget option.