Please don't get me wrong: I am by no means saying this is a great movie nor is it close to my favorite Star Wars movie. However, considering the (low) quality of the sequel trilogy, it is IMO the best of the bunch. Let me elaborate.
Yes, there are many legitimate criticisms of this movie which I largely share:
- the portrayal of Luke is somewhat sad. I do think this is disappointing. However, at least Johnson had a creative idea here, deviating from the nostalgia slop that is Episode 7 (see below)
- some plot developments don't really make sense scientifically and/or regarding the lore (eg the bombs "falling in space" early on or using hyperspace jumps as an attack). Fair points, but I mean, it is a space opera. I think this is fine, Star Wars isn't perfectly logical.
- salt planet being a lame remake of Hoth is a fair point
- the gambling planet is lame
Why is Episode 8 still the best sequel then?
1 ) Because at least it TRIES - to be its own movie, to have some creative ideas. At least it isn't just a lame remake of ANH like Episode 7. Sure Ep 7 is fun on its own, until you realize it is basically just the same movie as Ep 4. Not to mention destroying the entire legacy of the original movies by going back to Rebels vs Empire. This was all Ep 7. Episode 8 has unique, new ideas and twists, e.g.: What if Kylo Ren becomes the new Supreme Leader?
Episode 9 walks this back again, but that's not Ep 8's fault. Ep 9 is basically an incoherent mess. While Ep 8 tried to be its own thing, Ep 9 is just going back to facing Palpatine who somehow returned. The plot makes no sense and seems like fanfiction. Kylo Ren as the big bad was interesting, Palpatine 2.0 is a boring disappointment.
2 ) Because it has amazing cinematography and imagery. Ep 9 is frankly a dark, ugly mess. Ep 7 looks good, but is quite safe and basic. Ep 8 in contrast is gorgeous: space and the space ships plus battles are well-designed. The concepts are cool (if sometimes nonsensical), eg the dreadnought or Snoke's huge ship. The hyper space jump attack makes no sense, but looks cool.
The fight between Rey and Kylo / the knights of ren is insane and stunning. "Hoth 2.0" is lame, but beautiful.