First of all memes are not only ideas. These are two very different matters. So this analogy is no problem. Fast-changing memes are another matter. They are the thing you focus on when speaking about mutation-types.
Ideas can stick together in complexes, that are copied from individual to individual in one complex.
That is the idea of a meme. But memes can be shuf fled with other memes, in the brain, for some purpose, or without clear purpose. It is clear that the mechanisms working in this are different from the mechanisms of genetic re-shuffling. In many ways, that are fundamental. That should be clear.