Most people gave very good answers, I just give my 2 cents.
I don't think this is an issue as long as there is enough evidence all together. The separate bank accounts thing is common and you don't have to worry as long as you can provide other documents showing comingling of finances like joint tax returns, beneficiary 401K, Joint Investment Account and such. It's more about the holistic picture than each piece of evidence by itself.Basically if you lack in one area try to compensate in the other area. That said the joint account is a "Quality" Evidence and you can't replace it with like 100 pictures thinking they will provide the same effect.
Personally me and my wife did have joint accounts that were not "Active" but I provided joint saving account with significant amount, a joint mortgage, 401K stuff.