That's extremely uncharitable. I think slack and discord have pretty great UIs, and that's all "web tech." Figma just IPO'd at a $58 billion valuation - is that not proof their UI is good? If it wasn't good, no one would use it. VS code became the preeminent text editor and IDE over the last decade - all web tech.
Not sure about others but VS Code and Discord are slow and eating too much RAM for what they do.
Does that matter? The UI is great. Hordes of people agree.