The underlined statement is a bit inaccurate. macOS has built-in protection on several fronts: XProtect (since OS X 10.6 Snow Leopard), MRT (Malware Removal Tool), Gatekeeper (Since Lion (?)), SIP, and a couple of others that I am forgetting.
And, there is the T2 chip on newer Macs that, in conjunction with the operating system, locks out many forms of attack vectors.
Is it complete, or perfect? well, probably not! It remains your choice about adding third-party protection, I suppose. I like the free Malwarebytes.
Current version of Malwarebytes (v 4.1) will run on any version of macOS from 10.11 (El Capitan) to current 10.15 (Catalina), so Malwarebytes would be fine on Mojave.
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