Depends on the site. A lot of the image sites do that. Imgur is pretty responsive, but on here it gets a lot of hatred. Most of the poal-approved alternatives give me that same "too long to respond" behavior, and trying to upload to them is even worse. It's likely some poorly coded sites that lack storage, bandwidth, or error handling. That, or the secret whatever jew overlord o'bama techno glowbug mega script kiddie elites are blocking you from seeing some truth or something.