Haven’t done solo with ABD but have traveled through China extensively through the years including 1995 - a 2 week solo backbacking trip through central / southwest China in my early 20s.
Having been on Disney Cruises including a medical debark for my dad. The ship sent a castmember to be with us for the two days we were on Nasau. There is no way ABD castmembers will allow you to feel left out. Same with getting lost, but locals are so friendly in China that on the off chance you do get lost, you will get a lot of help immediately.
I just came back on a 2 week trip and 6 cities in China with my family of five and can confidently say you will be fine traveling alone in China, even if you weren’t with ABD.
We did China a few years ago. We did not travel solo, but another person did. I don't think she ever felt left out of anything. We often sat with different groups at dinner, and ABD makes it a very social event. She made friends along the way and seemed to have a very nice time. And the Chinese people are terrific. It's an amazing experience doing China with ABD. It would be way better to go solo to China than to miss out on the uniqueness of that trip - in my opinion!
I travel solo all the time (11 ABDs) and did ABD China pre-Covid. I’ve never felt left out. Other than breakfast, which is OYO in the hotel, all other meals provided are with the group either at one long table or different tables. As a solo traveler, you will never be put at a table by yourself. The guides do a great job of noticing who gels together and matching them up for activities or seating them together during meals. For the OYO meals, you are free to do your own thing.