This is all rather interesting and a bit confusing. As per official golang docs:
Go 1.20 is the last release that will run on macOS 10.13 High Sierra or 10.14 Mojave. Go 1.21 will require macOS 10.15 Catalina or later.
and indeed binaries for 1.23 officially provided do not work on macOS 10.13 - the same with official rclone built using official go, however... when go is built from source on such older system all is fine and working.. As I proved earlier building go 1.23.4 and latest rclone.
So it is either some real limitation (can't find what it is though) which makes them to drop old macOS support or simply nobody is interested in even checking old and obsolete OS versions and they build it with such support explicitly disabled.
BTW - you can make rclone mount to work as well. It needs macOS FUSE which works even for macOS 10.9 and then compile latest rclone from source (not via brew which disables mount). Of course using go built on the same platform only.
On the other hand it is impossible for rclone officially keep supporting what go is not. It would be too complex to use and maintain workarounds and given that it is real niche issue it has to remain as it is. Good news is that unofficially users can DYI rclone on these older platforms. Hard to say without trying how far back it can be done. Would macOS 10.12 still work? maybe even older?
I think this thread deserves to be moved to "Howto Guides" category. Hopefully it will make some old Apple computers users happy.