It has enormous speed bottlenecks. Im not sure if its joomla, apache, or mySQL. Or maybe its all three. The core joomla, in my opinion, is a good foundation only if one wants to spend a zillion hours rewriting / modifying its code. Thats sensible for some. But for business minded people with little to no programming abilities, it can be a waste of time. Joomla is scaleable but its only as fast as the hardware in use will permit. With all the various developers using their own ideas and mechanics, its no wonder a joomla site can be brought to a crawl. I think a more modular approach, with a keen eye toward scaleability and speed is whats needed now. There are a lot of rubbish components out there because some developers refuse to adhere to proper php, mySQL, and framework guidelines. I only wish i could put together a project that could reinspire joomla artists and technicians.
Change the world one step at a time.