I never believed (and never been told) that silicones in itself are bad... the only problem is the washing out. Silicones in itself are good I think, they hold moisture and provide a lot of slip. They also protect from heat.
Even if you can use coco betaine to wash them out, I still think co-washing is better than low-pooing... but then again, that depends on the person. My hair is just never greasy... sometimes I do low-poo though, when I've used a lot of oils and right now I'm temporarily living in a hard water area so I need to get rid of the build up every now and then.
I'm not going to use silicones, because I don't want to be dependent of low-pooing. I'm alright with low-pooing every now and then, But I still believe co-washing is better.
But of course, all hair is different, and everyone should do what they found out to be best for their hair