It depends. I have no idea why Microsoft Teams has such terrible performance on my Mac, for example. Slack is perfectly performant.

If there's a general ("inevitable") reason it's that updating the DOM (i.e., adding, removing, and changing HTML elements) is very slow compared to the function calls that native apps use to draw on the screen. That's why frameworks like React are designed to update the DOM as minimally as possible. It's also why Figma is written in C++ that compiles to WebAssembly and draws its content with WebGL instead of using the DOM.