Since you do not have a smartTV, one of those boxes is exactly what you want. TLDR version:
AppleTV: if u want to show youtubes from your phone/ipad to the TV to guests ( i think, i don’t use apple)
Roku: best interface. best search. universal search. It means you just hit search, type in name, it’ll find it on netflix, hulu, whatever you have. The remote even has a built in headphone out for late-night watching.
FireTV: it’s cheap… modable. UI sucks. I use it.