I was a linguistics major in college and if I learned one thing during those four years, it is that language changes! Can you imagine if someone put Plato in a time machine and he was forced to get around Athens today with his ancient Greek? (It would be “Greek” to him, ha ha.)
Language changes are inevitable, and I think throughout time people have always gnashed their teeth and pulled their hair out over how their language is going to pot. But most of the time, I don’t think there are any inherent “good” or “bad” qualities to language change. For example, did you know the word “apron” used to be “napron”? But many people heard “a napron” as “an apron” and started using it that way. Now, I bet at the time, there were people who were FURIOUS about this – it’s not “apron” it’s “napron,” darn it! But does it really matter? Not really.
Another example: English used to have a sound made in the back of the throat like the German pronunciation of “ch” in Bach. Words like “through” and “bough” ended in this sound (ever wonder why there is a “gh” at the end of these words? That’s why!). But nobody is advocating to put that sound back into the English language. That would be silly.
English used to have all kinds of case distinctions, genitive and whatnot, like German still has. Most of those have been lost, which has made English sentence structure more rigid to compensate. But there are still some residual case markings on a lot of pronouns. For example, you change the first person pronoun (I/me) depending on the case, but you would not change a noun like “fish” depending on the case. “I want it/Give it to me” vs. “The fish wants it/Give it to the fish.” (In German, “the fish” would be different in these two sentences.) Some of those rules with I/me are breaking down because they are just residuals of the former case distinctions anyway.
I don’t think it really matters that much, as long as you can express yourself effectively. For the most part, educated people know when they can get away with saying “me” and when they should use “I”. And sometimes, people will think you’re an ass if you say “I” – according to the classic rules of grammar, if you knock at a door and someone asks, “Who is it?” you are supposed to respond: “It is I!” But unless you are Ivanhoe or someone similarly important, you should probably just say, “It’s me.”