Google Chat is definitely a product that could use more love, but it is situated in a specific internal landscape, and grows out of it. Slack is built for a very different context, and I doubt Google would build something like that. Google simply doesn't see the world the way someone who likes Slack would (and I also doubt a large co like Google could operate out of Slack).
Such as who? And are most of their employees actually using Slack or are a few white collar employees using it while 90% of their workforce has no idea?