I think it was more of the surface. Maybe the humidity played a role also. My wife wore sandals and it didn't seem to affect her as much as me. I had on pretty flat nike sneakers so I'm sure that didn't help.
The stairs and area getting into the main pool were also slippery. It's like a cushioned rubber floor with no texture for grip.
I was on the 8/31 sailing. The lines were there depending on the time of day but they moved pretty quickly. When we did eat at the buffet, I mostly grabbed food from the deli as that seemed more appetizing to me. I would recommend the MDR.
The lido deck and buffet area is SUPER slippery. I wore sneakers and was sliding with almost every step. Definitely need to walk slow in certain areas.