When HD Was Being...
...specified, the Society of Motion Picture and Television Engineers (SMPTE) determined that 35mm theatrical projection was the "Gold Standard" that audiences would expect.
Therefore, they applied (then) modern TV measuring methodologies across the entire bog standard Hollywood workflow.
The results measured the theatrical experience as 800 TV lines horizontal resolution. TV lines, in this context, are actually line PAIRS, so that translates into about 1600 horizontal pixels.
That was the optimal. In the real world, additional artifacts due to dusty projection booth glass, worn projector gears and film paths, damaged screens, platter scratches, etc. reduced the resolution and clarity of the movie experience.
If you saw a 70 MM print in a well maintained theater, your experience would approximate 1920 X 1080 on a well designed home system.
Your screen will definitely be <em>showing</em> "new things within the movies now that we've never seen before..." Whether you see them or not depends on how much your eyes have deteriorated in the intervening years.