In layman's terms: we're working on it.
A slightly expanded version would be, our traffic and posting volume has increased by about 50%. We'll catch up.
As for slow, well, it isn't consistently, is it. For example, at the time you posted, I checked and I was getting pages in under .3 seconds. There are occasional ephemeral events that slow everything down and we're working on eradicating them.
Now, in laymans's terms, can you explain why I can eat the same diet everyday and most days lose a little weight but on a few others I gain a bit? Hint: complex systems don't always work in a consistent, linear fashion ;-)