No, it's not impersonal. The way to show newcomers that they are welcome isn't with a faux-personal greeting, it is through the policies, tools, and other mechanisms your team is creating. (Thank you for your work!)
Think of a retail store that has a big welcome banner in the parking lot and a sign saying "customers are #1" at the front door. And yet the floors are dirty, employees are grumpy, and the shelves disorganized. All the word-smithing in the world can't overcome the customer's actual experience. Fake friendliness in online communication is obvious and insincere. For example, sending a message to Google or Facebook, only to receive a one-line reply saying, "Your feedback is very important to us." HA! It just went in a bottomless pit never to been seen again.