Something worth testing is to open the same extension or model in a browser. If that is a lot more responsive, then there is an issue inside SketchUp that could be improved. If it’s slow in a browser, either your Internet could be better, or the web pages are too demanding.
For me, the initial window takes a while to fill in, but then going between pages is about the same in SketchUp as it is in a browser.
Extension Warehouse is slow, utterly slow. I try to find something else to do to pass time while it’s loading, e.g. browse the forum. Haven’t had any problem with 3D Warehouse though.
being that there are people responding to the issue talks for itselft. but to clarify my point, it does not really matter if you open them in su or in a browser… its a generall performance issue.
thanks for considering this worth an effort for the future!