> Honestly I have never really found a situation where I wanted to exactly (or even slightly) mean reduce by 10%. It is too specific of a definition to be truly useful.

I hope you realise that your use cases for words isn't the same as every other English-speaker's.

> I find it much more convenient, and useful, to have a word that means the current modern definition of decimate.

The word you're looking for, as mentioned, is devastate. Perhaps ruin, destroy, wreck, ravage, desolate, demolish, raze, etc. If you're happy with a phrase rather than a single word there's plenty more to choose from to convey your desired meaning.

> Perhaps decimate is a poor choice to represent that, but honestly not every word has to sound or have roots that directly relate to the definition of the word.

Agreed, but where words have a specific use (even if not to you) it's frustrating to have their meaning modified to a concept that is more than adequately conveyed by dozens of other, existing, commonly used words.

That's my point.

> It is more important words are used, rather than languish or die in history books.

I'm not even sure what to make of that claim.