The problem is that Time isn't something they seem willing to give to the cat. A cat is a box of surprises. Sometimes we get the easy ones, sometimes we get the ones that require more dedication. Getting rid of one and getting another is no sure answer to our problems. Like I said, it's give and take.
If anyone is not willing to be challenged, then he better not get himself a four legged companion.

So Joeye, before you think of sending your cat to the shelter, give him a chance, try to find out what makes your cat feel calm, use positive reinforcement, try to find the answers to her meows, get some toys around, a scratching post (can even make one yourself), keep her busy.
But be aware that there is a chance that your cat won't change, that he will be a talker for the rest of his life. Be also aware that if you win this challenge, you'r likely to have found yourself a wonderful companion.

If you think you'r not up to it, then do your very best to find MishMish a HOME (and I mean a real home). It's the least you can do.