1. aiming a missile and beating a jedi is something totally different. luke could not beat Dart Vader in Ep.V and Ep. VI.
2. they could jump to other system and than jump back or they could ask other destroyer to jump into system in front of that rebel fleet. And still they could deploy the tie squadrons, there had to be hundreds of ties in Supremacy.
4. the official statement from disney was, that Snoke is stronger than Vader and Emperor.
5. and what luke, finn and other learned from their failures? Only character making any psychological progress is Poe.
8. no, the only statement supporting your statement, that mark is OK with the movie was the one from 26th December released on his twitter, which in my opinion is only damage control from Disney. He repeatedly said he does nt like the story of his character in episode 8 and if you saw his reactions after the premiere, than there is no doubt whether he was happy about the movie or not.
As per what would I do, I am nto a screenwritter, as Rian, but should it be on me, I would at least try to come with a plot and use the plot points I have from Episode 7. He just negated everything new and obscurely unexplained. Who is Snoke? Noone. Who is Phasma - not important. Who is Rey - Noone. What did Luke do all the time - nothing. What is the political story behind FO - not important. Where are the other Empire officers escaping to Unknown Regions in Aftermath - not important. Who are Knights of Ren - not important. Do we have any new character or plot point? No. Did he managed to settle the death of Carrie Fisher? No. etc. etc.
Do you want to know what would be cool story for Last Jedi? Just one idea right out of my mind. Let Rey fall to dark side with Kylo Ren manipulated by SNoke, bring the ******* Thrawn from unknown regions as an emissary of Chiss as a support force against the Snoke, let the Thrawn and Luke join together, Luke challange the Snoke resulting in death of Luke in combat but turning Kylo Ren back to light, so he is the Last Jedi, fighting on the side of Thrawn who fought on side of Anakin Skywalker against Snoke and Rey in Episode IX.
I have seen again for tenth time or so Rogue One and that story is so much better than Last jedi, that it is unbelievable, that it was produced by same company. Empire beeing dangerous and threatening, space battles making sense, decent humor for adults and psychology of characters making sense... omg.