I am having the same problem. Nothing helps...
Having the same problem since tvOS 13.3
Same problem here.
Subtitles are very small and cannot increase the size of the subtitles through the Apple TV settings
This makes it near impossible to read the subtitles on a small tv.
While Netflix is the no 1 app we use on the TV box, it makes the Apple TV box almost useless
Please fix this, it is so annoying
I restored tvOS 13.2 and size of subtitles Netflix are large again
I used the explanation from this site https://support.itsolver.net/hc/en-au/articles/360000299936-Downgrade-tvOS-13-to-12-on-Apple-TV-HD-and-4K
and used the "tvOS 13.2 (17K82) for Apple TV 4 (2015)" firmware on https://ipsw.me/AppleTV5,3
and set autoupdte on "Off"
having the same problem. Nothing helps
New year and old problems, still not corrected the issue... strange is that in my case the subtitles change the format (shade, borders) but not size.