Travelling to Mt Aso

Hi, I am planning a trip to Mt Aso in early Dec. The website contains the below information:
"Level 2 Eruption Warning.The area within 1km from the creater is off-limits."
But I'm not too sure what does it mean. Is it still worth a trip there?
Will the sulphuric smell be strong? I don't intend to do intense hiking though.
Thank you!

It means that you could not see the crater from up close, as explained here:
https://www.japan-guide.com/e/e4552.html

I personally think that the surrounding scenery is still impressive enough to make the visit even if you cannot go to the crater.

The smell of sulfur won't be strong, since you'll be kept away from the crater rim. Unless the situation improves and you can go to the rim (frankly, I wouldn't get your hopes up). There is everything else still there though. If you want to go hiking, you still can.
How are you going to the Aso area? If by car, your options go up immensely. Seeing the Nabegataki Falls is wonderful. There is also the Daikanbo Lookout, and Kurokawa onsen if you'd like to try some outdoor hot springs.
https://goo.gl/RwpnU8

On the main webpage of this website there is a video of a 3 day self drive through Kyushu. The traveller visit Mt Aso. Maybe use this tool to decide if Mt Aso is still worth it for yourself.