Alright, I'm going to explain it once again:
A lot of people will use an LFD tool. There are reasons for it.
1. It will make grouping easier
2. Feel free to use the trade chat for group searches. Let me know how long and how well it worked out for you once you get silenced due to spam reports...
Using this kind of Addon in Vanilla within the mechanics of Vanilla is not a problem:
1. You'll still have to interact with people
2. You still have to travel to the dungeons
3. There are no crossrealm functionalities
Oh and you know what? YOU DO NOT HAVE TO USE IT IF YOU DON'T WANT TO! It is your choice whether you install an LFD addon or not...