I was thinking about what a thicker cable does to the signal. I don't know enough of these things, tbh. School was a long time ago.
I am not so worried about skin effect as some are. To me it seems as if skin effect is mostly an horror in the transmitting of "higher frequency" signals, such as radio or worse, video, in the analog realm. I still have to find if the larger cable can actually contribute to a significant loss when it is mainly digital media passing down a line that is already nearly saturated with other specific digital media.
I need to look into this some more.
This is why they sell such expensive cables which have silver plated conductors and teflon insulators, you know. They are fighting against the property of the signal being radially dispersed in phase due to cable gauge. Phase integrity is essential in a transmission line where data must be kept within a certain range of phase differential before distortion and losses add up to a substantial portion of the total signal. Honestly, I may need to find out more, but at eighty feet, before I even separate the cabling into the spaghetti that goes to all my stuff, I can not see how RG11 is itself a problem.
Your instinct that the cable company used shitty splitters (and I know for a fact that they did not install a single amplifier in the entire system) and connectors has me really thinking, though.