Most of my review consisted of explaining that conclusion. Also, I worded it that way to avoid calling it pretentious because I didn't want to go that far. I want to believe that Tarkovsky was just too focused on being artistic that he neglected pacing and viewer patience.
You describe scenes you felt too slow or boring, but you conclude there was an intention of being artistic/slow for the sake of being artistic/slow. To get to that conclusion, you'd need to either discuss Tarkovsky's intention (which you don't) or to attribute an intention to the film itself (which makes no sense).
I will not go into an exhaustive comment about
Solaris (I haven't seen it in about 10 years), but one thing about Tarkovsky is that he is looking to liberate the eye and attention of the spectator from the constant control of common narrative cinema. You watch
Mission Impossible 5 and your eyes are dragged to certain precise parts of the screen at any moment. I think that it's in
Poétique du cinéma that Ruiz tells about his first experience in an American editing room, where he'd point continuity errors and jump cuts to the editor and the editor would just not care, saying the eyes of the spectator would be drawn elsewhere in the screen.
The average shot length is now below 3 seconds (and that length normally grows in relation to the shot's content - about 1,5s per additional character in average). Having over a minute to watch a shot, with no action to direct your gaze, being constantly forced to consider the shot's composition and to feel it's duration, puts you in a different position as spectator. You can go through a Museum in 10 minutes, or you can appreciate art. Tarkovsky sits you down and forces you to think about his films, and about your position towards his films. You can think they're boring - he didn't think
Solaris was that great himself - but you can't refute their efficiency.
Here's an example. I disagree with pretty much everything that's being proposed in this video (or maybe it's just very badly brought forward), but still, it's pretty clear that Tarkovsky's pace forces this guy (and every serious spectator) to think about what he is seeing beyond the simple narrative level of the film.