There's several issues involved there. For starters a "human rated" rocket needs to operate within certain performance envelopes and have certain features. For instance the rocket carrying a human crew will have different vibration needs than one carrying cargo. The rocket also shouldn't vent cryogenic gases to the atmosphere while on the launch pad which creates a danger for astronauts and a ground crew when the rocket is fueled.

The Ariane hasn't ever really gone through a human rating process and doing so would take several years. Even then, the ESA does not have a crew launch vehicle available. The Automated Launch Vehicle was used to resupply the ISS but can't carry a crew despite having a habitable volume when it was docked to the station.

The ATV doesn't land but burns up in the atmosphere at the end of its mission. That's not a vehicle astronauts would really want to ride home in. While I don't doubt the ESA could develop a manned vehicle, it would just end up being so different from the existing ATV that it would take longer to develop than the remaining life of the ISS.

That makes sense. I don’t follow this stuff closely but o didn’t think they were moving people yet.

That would be a great alternative but they could end up in a situation where I’m once it’s ready it takes a while to shake out too.

So the US may not have that option for quite a while. Or maybe they can’t launch frequently enough when they’re ready.