Yes. Consider a book. Can you tell if it's a cyrillic or a latin `a`? Of course you can, because of the context. Unicode is about visible text, having hidden semantic meaning makes it something else.
Besides, 'a' can have all kinds of semantic meanings - all depending on the context in which they are used. There is no way to encode all this into Unicode.
> If they did then there's no consistent way to group those two alphabets
Doesn't matter.
> And what happens if the shapes of those two characters divege over time?
If it actually looks different, then it becomes a different code point.
> There are characters in Chinese and Japanese that share a code point but the shapes of the characters aren't the same in the two languages
More evidence that the Unicode committee lost its way.
Think of it this way. Printing Unicode text on a piece of paper, and then OCRing it back into Unicode, should be a lossless operation. Or another way - anyone should be able to tell what the code point value is by looking at the visual representation of it.