Although possible to disable the feature, those steps are crazy complicated, and probably impossible for anyone who isn't a developer. (Apart from anything else, regular users should never be advised to disable SIP.)
A year ago, a Chrome update (its Keystone auto-update agent) corrupted system files in Macs which had SIP disabled [1]. The result was that they didn't boot anymore. Mac users who had SIP enabled were not affected.
I won't disable SIP and I'll avoid installing Google Chrome on my new Macs, if possible.
What stops a Linux program altering the system? I guess you need root access to change things outside of /usr/local this could easily be done on macOS too but the wheel had to be reinvented by Apple in a way that is probably less trustworthy.
With SIP you can't change some things even as root. SIP has definitely made macos a harder target, though it is still lagging Windows in some areas. Linux is almost comically unprotected.
You can check binary signatures on disk (tripwire) but that is extremely tiresome to maintain and does not prevent straight loading of shellcode into memory.
/usr/bin/vim was installed by my package manager, but there's no guarentee the version I'm running matches the version that was installed. Now in debian there is a file which has a checksum of the version the package installed, but that's not checked on execution, nor is it itself signed (so the process that replaced vim could just as easilly replace the checksum, or the process that checks the checksum)
You actually need root on macOS to modify anything under /System, and this was the case even before SIP. This is why some installers ask for the root password.
