I guess we have to live with many of the changes - language grows and acquires new words and expressions. I love the way ordinary words have new meanings since the computer age, such as 'mouse'.
There are lots of different 'Englishes' nowadays: African, Indian, American, Scottish, English and others. I think that mass communication is probably keeping the language together: instead of American and English growing apart decade by decade, as they would without all-encompassing communication, they just absorb bits from each other (alas mainly from the US to the UK) and remain the same language.
Think of Latin: it evolved separately into French, Spanish, Italian, Portuguese and Rumanian - probably others I've forgotten about. If they'd had the telly, radio, telephones, air travel etc all those countries may well have spoken the same language but with different accents. Just a thought - I might well be wrong.
Oh, about chemist v pharmacy - I agree pharmacy is more accurate, a chemist can be many things. When my brother was an engineer with the water board, running sewage works, his best mate worked there as a chemist, but he always called himself a 'shit tester'. I guess he went for accuracy too!