Why is this considered as one of the best movies of all time?

Rating: 4/10 (1 September 2019)

This movie was a boring mess. No subtlety that would suggest what "rosebud" means or make the viewer realise by the end what that actually meant. So yeah... it supposed to mean the fact that chance played a big role in the outcome of Kane's life. But where is that ever mentioned in the movie? Where is this theme ever hinted at or discussed maybe by characters? It's just supposed to pop up in the viwer's head by the end of the movie?
It didn't pop in my head, and I wasn't impressed by this movie. I fell asleep halfway through and had to wake up and continue. And apart from a couple of scenes of good dialogue, good performances from the actors and very good cinematography, this movie was a total letdown and a slap in the face towards anything a good movie should be about: Great story, great dialogue, great performances, great direction, great technical stuff, inspiring, thematically deep, intriguing and entertaining. Unfortunately this movie succeedes in only 3 of those things I've mentioned. So my rating will be acordingly: 4/10