How can people just identify bad acting and bad writing in movies?

A lot of times on Reddit and YouTube I see people criticizing and bashing movies left and right (both old and new) for bad acting and bad writing. How can people identify that so easily? Whenever I watch movie I can seriously not identify any of this, unless it's like a really bad production like The Room.But most of the time I don't hear this about films like The Room, but rather the latest blockbuster or even arthouse films. People are always criticizing them for bad acting/directing/writing, but how can they do it so easily and what does it mean? When I see one of these movies, I never can identify this, everything feels okay to me from the actors and the writing and directing, I don't really notice all of this bad stuff, or even know how to explain it if I saw such a thing.Sometimes the movie barely even came out and on Reddit I already see comments saying the acting, the directing and the writing was bad. But they rarely say why so I get really confused about what exactly is wrong with it? And even if they do elaborate, which isn't all the time, I don't really notice the things they're saying constituted bad writing and acting in the movie.Does someone feel the same way? via /r/movies https://ift.tt/3kVX9Zl