Applications have to be signed now (unless you explicitly turn off all protections), yes, but I think GP is referring to Gatekeeper — which would prevent a file from executing unless you right click and choose “allow” for programs from an unknown developer. But a right click could get it to run. Now applications need to be notarized with Apple in order to work in macOS (unless you flat out disable all security), which adds an extra burden on developers but ostensibly offers much more security.
Does it tho? In what way? Anyone can create or steal a developer account. You can still notarise malicious software. It just that it gives some lead for investigators to follow (for couple of cases per year that are significant enough).
p.s. how App Stores were designed by accepting binaries rather than source code for review is beyond me. Such an obvious oversight.
