Are the channels you are getting Digital or Analog OTA? I'm not sure how it is for the 5010, but for my 151 there's an option to switch between the two. The button my remote is DTV/TV. Check to see if that's the problem.
Honestly, digital SD channels should still look pretty good on the 5010. 50" for 10 feet away is not too big in fact, I, personally, would even go with a 60", but that's just me. Also, will you be getting a blu-ray player? Why is it going to be solely non-blu-ray viewing?
LG OLED65C6P / Marantz AV8801 / D-Sonic M2500 / Oppo BDP-103 / PS4 Pro
GR Research LS-9 / GR Research X-Voce / GR Research AV-1RS / Oppo PM-1