Displaying 3D geometry in a browser is different than manipulating geometry in a browser realtime.
A browser is not a dedicated app optimised to handle a specific 3D task like modelling or uv mapping etc.
A remedy would be to start with a file with untextured geometry. That would provide you with a performance baseline on how the web based version handles just geometry of a typical 'Liam' file.
If you see noticeable improvement then you could surmise that textures are impacting performance. Then make a pass on your textures to reduce their footprint and see if that improves performance.
But the short story is a web based app is not suited to a typical use case. Even though it accepts 100mb file upload sizes it is not guaranteeing you can work the file to same degree as the desktop app. Similar to how my TV remote has buttons with numbers but its not a calculator.
Horses for courses...