For me, someone who has flown the 763 a lot this year, I haven't given up on the lavatory in C-hardly ever a line for me.

Sure, I wish they had a rope or the curtain divider back but I haven't ran into any problems because of one reason: FA's

Almost all of my 763's have been international or transcons, I am not sure there is a short-haul 763, and everytime I walk back to use the lavatory in C (from my standard seat 8A) I always see one or two FA's sitting, chatting, reading in the jumpseat that is set between C & Y. That FA acts as an enforcer and denies the rule-breaking Y passengers access. Does it always happen? No. Could it be better? Yes. But remember there are only 2 lavatories on the 777 for 49 passengers so the 763 still gives you a better ratio than that.