What was wrong with using classical character sets for databases?

Classical character sets only handle a few languages at a time. Mixing languages was very difficult or impossible. In today's markets, mixing data from many sources all around the world, that strategy for products fails badly. The code for a simple letter like "A" will vary wildly between different sets, making searching, sorting, and other operations very difficult. There is also the problem of tagging every piece of textual data with a character set, and corruption problems when mixing text from different character sets.