That response from the hosting provider is so funny it is ridiculous. Think about what they are actually saying.
We have hosted a CMS package that is so poorly written that in order for it to run at a more optimum speed we need you to install more software that needs to be loaded with the CMS system in order to make it a little more efficient as it loads.
For anyone that has studied Computer Science in college, does loading more software into RAM, requiring more processes to process that software, really increase speed. Everyone with a engineering background knows the true answer to that question. Of course not.
We can play with the cache, we can bump up the threads, we can dedicate more RAM, we can increase the resources but eventually it all comes back to bite us. Those packages, Joomla, WordPress and the rest serve a purpose, they are meant for individuals that have no idea how to program, they do not want to learn how to program and they want a site up and running as quickly as possible.
At what they do, those packages are good. But they are inefficient as hell. They are poorly written, they have way too many plugins and addons, which oh by the way just add to the problems with speed and efficiency and everyone expects them to run like a stand alone CMS, they never will, accept that.
With the speed of deployment, bloated code, and support for the millions of people making a living through the add on products to support those systems they are what they are. These systems have created a whole industry around them. And you thought they were FREE.
If you really are that unhappy with the speed of your system, develop your own CMS. It is not that hard, especially with some of the good frameworks out there in HTML5 / CSS3. There are a ton of us that will help you out if you need it and then you will get what you really want. A fast, efficient, and manageable blog that you will have complete control over......