Lots of developers think that. When you've got a working mental model of how software functions, generally, you interact with computers completely differently. Most people don't even think about 90% of the interfaces they use— from text messages to microwaves to ordering kiosks to car radios— specifically because UI design is light-years beyond what it was. You want to see what usability looks like without interface design? Look at FOSS... And guess how many non-developers use end-user-facing FOSS apps? What about big ones like Firefox and Blender and Signal? As in, the only ones that have any nontechnical user base? They're almost exclusively run by foundations that employee product designers and UI designers for their important features.

As much as developers like to imagine they're somehow experts on interface design because they've used so many interfaces and understand the tooling, empirical evidence points to the contrary. I worked as a developer for a decade before I moved to design, and I hate to say it, but damn near 100% of the confidently stated interface design knowledge among developers is because they haven't learned enough to get over the dunning-krueger peak, and echo chambers like this only reinforce that.