I'm not sure that "outdated" is the word I'd use. They're "old", certainly, having been around since the 1970s! It's rather that there are a lot of other options these days, and the 40xx series chips aren't the best for every situation.
They're still available, still cheap, and still do the job, so sure, use them if they suit the application. For certain things, they're a nuisance, since they only cope with a 15V power supply, which often means you need to set up a 7.5V bias level just for them, and then have everything going to the switch chip with DC-blocking caps both in and out. That's annoying. Plus the switch signals have to be full voltage - you can't switch the switches with 5V logic. Of course, if you're controlling it with 4000-series logic too, no problem. So it depends on the situation.