Here's a fantastic example: sentient, sapient, and concious. These are VERY different words with wildly different meanings, but they're practically treated as synonyms in colloquial usage. The only way to properly express them now is to use their entire definitions, and then people question why you're being so specific or excluding certain things.

What if you just think of it as our culture putting less emphasis on the concept of “literally” and more on “figuratively”. And the evolution actually makes the language more expressive, given the things that we’re trying to express (on average).

I don't agree that it decreased the total expressiveness of English, no. The modern colloquial use of "literally" is not identical to "figuratively", or to "very", or any other word I can think of - it's an intensifier with a unique connotation that doesn't have any good alternative. At worst, we have lost some expressiveness and gained some expressiveness, and there is no objective metric to decide whether that's a "net positive" or a "net negative"; it's just a change.