No pun intended - this can be seen as a love letter. I would argue not just for Korean cinema (movie making that is), but any all over the world. But of course there are certain things that may be particular and just more on point there. It does play in the 70s, so I assume some things may have changed since then - one would hope so at least.
All that said, great acting - within acting - and movie within movie and all that. Though as is true with almost all movies that have a movie as central theme ... you have to suspend your disbelief ... as in making it non existent, if you catch my drift.
You could argue that we do not see the movie, but a spectator perspective ... fair point, but you mostly do not see the work that has to be done between shots. But that would kind of make the movie a drag ... this is about something else ... about a dream .. about showing critics that things are not as easy as they may think they are. Plus a lot of personal stories of course! May be a bit too long - and I was a bit surprised with the ... let's call it addition in the end ... but I reckon it was necessary ... to give us something back.
Well done to say the least - and realistic in a way (relationship wise), in a very unrealistic way - gotta love it. Also not to be confused with the American Cobweb ... renamed Knock Knock Knock in Germany ...