Using SCSS and using some utility classes isn't in any way mutually exclusive. If anything, it's a lot easier to mix and match. The argument isn't against having utility classes/mixins/extensions in general, but against relying on them solely.
I'm still not convinced — using only utility classes has very clear downsides, while using what's reasonably one of the most common approaches in the industry right now avoids those downsides while also providing additional benefits.