I disagree. You start the story where you want to start it. And you explain through exposition or by action in various scenes what the current galactic situation is. How many movies start at zero and build up? Many start with characters midway, on some level, and we learn through dialogue, flashbacks, or even prequels, more of the backstory. Let's look at sci-fi films that take place in the future, for example. Rarely are they going through a detailed backstory to show you how things got to the point that the story starts. Some of that is handled in text before the film, a voice-over, or the most imaginative (IMO) was the opening in the Valerian film (and that took place in like 5 minutes or so at the start of the movie).
I don't see this much different than the new continuity being created now, which is filling up the space between ROTJ and TFA, or the side projects which fill in the backstory for characters. I think currently there is a Poe Dameron one with him talking with Rey and Finn post-TLJ. By the time Episode IX comes out, do you really think people who haven't read that comic will even know it exists, or think it has to be read to understand or enjoy the movie.
The MCU has like 19 films now plus several television shows and I think tie-in comics are at least quasi-canon. Do you think that's stopping the vast, vast majority of fans who haven't watched all of the previous films from enjoying each installment? Further, the MCU is based on decades of stories. The Infinity Gauntlet is over 20 years old. And even the more recent Infinity event is like three years old, but did the legion of moviegoers rush to the bookstore before going to see Avengers: Infinity War? No, they didn't. The film likely did increase business for the comics, and I think it will increase business for the comics after the film also, as fans might be looking to read the original source material to see how that story went or for clues for Avengers 5.
The sequels haven't even featured (or even mentioned) Coruscant, or included Lando for that matter, and while there are questions raised online about the absence of Lando, among others, these questions have not stopped the sequels from making massive box office. Star Wars does have now, as it did with the EU, more room to include/remove things, or hold things back because they do have a strong presence when it comes to other canon media, where we get Phasma's backstory in her own novel for example. And even with the new canon, it has not resulted in the world stopping as people feel they must read the Phasma novel before seeing TLJ. Or the prequel novel to Rogue One, or the current lead-in novel Last Shot for Solo.