Taking the films one at a time:
The Force Awakens: the chief and obvious source here is the Legacy of the Force/Darth Caedus; I think it's significant that Legacy of the Force was among the last stories, both written and chronologically, for the old EU. The only major stories after it were a) the Legacy comics, completely unrelated and set about 100 years after all the characters we know died, and b) the Fate of the Jedi series, which revolved around Luke and his son hunting for an evil... honestly I don't even remember what Abeloth was supposed to be. It wasn't a great series, and wouldn't contribute well to a film on the Good Versus Evil model, so my guess is Abrams just looked straight past it. (That said: Ben Skywalker did acquire a Sith girlfriend during the series, so maybe they took some pointers from it after all.)
Legacy of the Force is the story of the fall of Jacen Solo; I think (suitably compressed) it could have made a very interesting film series, but to do it properly, you'd have to start off with no proper villain. It would have given us an Episode VII which was mostly a political thriller, which, uh... "The taxation of trade routes to outlying star systems is in dispute..." Maybe not. Given the sort of films they were making, this was a pretty good course to follow.
I think The Force Awakens (it's even a similar title!) was a well-written 'sequel film'. The complaints about it afterwards were mostly a) Rey iz a gurl onoes ([Serious eyeroll]), b) it owed a lot to A New Hope (I guess, but not as much as the complaints would hold), and c) it didn't massively infodump every tiny thing it introduced (can I reuse that eyeroll here?). I don't remember any issues with the tightness of the plot, and we did rewatch it recently, so I hope I would.
The Last Jedi: Saying this up front: I think this was the best of the sequel trilogy. I have no truck whatsoever with the complaints that it 'didn't feel Star Wars-y'. I understand some of the things that led to them, and the only one that doesn't wind me right up the wall is the fact that it uses a lot of sacrifice plots, while SW generally only uses risk. But sacrifice - not 'this might kill me', but 'this will kill me/destroy the life I've made for myself' - is a constant theme in the X-Wing books, too. At least 3 of the 13 original members of Wraith Squadron sacrificed themselves in one way or another, and I suspect it's more.
I have no evidence beyond the films, but I am convinced that Rian Johnson was a fan of the X-Wing books when they were coming out. You couldn't adapt the books directly to film (they all concern fairly small-scale action, and are written to largely stand alone), so using their themes and attitudes so thoroughly was a brilliant way to make use of them.
The one plot point I remember people calling out as badly plotted (as opposed to 'I don't like it') was the side-trip to Canto Bight, but honestly, a) it doesn't take up that much real estate, and b) as Jyn said in Rogue One, "Rebellions are built on hope". Poe and Finn put together the Canto Bight plan because they lost hope, so it's entirely fitting that it failed and actually made things worse. (Though of course, the ultimate consequence was the Holdo Maneuver, and the destruction of most of the First Order fleet, sooo...)
The Rise of Skywalker: okay, this just came out, so I'll give you a couple of lines to run away from spoilers.
Oh gods. -_- The plotting on this film was... not great. It started with a massive infodump in the opening crawl, and yeah, there's a lot of decisions made on the basis of the script. I think what we saw here was massive 'course correction', because Abrams/Lucasfilm looked at the response to TLJ and decided people hated innovation, and so they needed to double down on the 'Just Like the Originals' idea.
Given that, I'm not at all sure they did deliberately borrow from the books I cited. They may instead have just followed the same thought processes: Dark Empire was (I think) the first big comic event, and Jedi Prince the first kids' book series. That meant both of them leant hard on material from the films, bringing back or heavily referencing the villains in particular (the latter series features Jabba the Hutt's... uncle? Nephew? Something like that.) Abrams may just have been following the same course.
It wasn't a good decision. Then again, following the plot of the 'source' books wouldn't have been, either. A better choice, actually, would have been to go back to the Jedi Academy trilogy. If you combine it with its indirect sequel, Darksaber, you have a story where Kyp Durron returns to the Light because of personal loss, and another of Luke's students dies to throw a fleet of Star Destroyers out of the system. Combine the two, and you can write a story of a tortured Kylo Ren agonizing over the loss of his master and his parents, being ousted by General Hux, joining Rey and the Resistance to fight the First Order, and sacrificing himself to destroy them through an awesome display of Force power. You can even throw in the goofily-named stealth-armoured Super Star Destroyer (K)night Hammer for good measure.
It's far from the only film that would have worked, but it would have been a sequel to The Last Jedi, rather than a fight against it. (I've described Rise of Skywalker as being the result of Abrams having the whole trilogy planned out in his head, and just straight-up ignoring the fact that he didn't make the middle film.)
Final thought: a whole lot of the books I've discussed make use of terrifying women in Imperial uniforms. The X-Wing books featured the cold, ruthless Ysanne Isard running the Empire; the Jedi Academy trilogy found Admiral Daala hiding away, unaware the war was over, and wreaking galactic havoc with her fleet of four Star Destroyers (yes, only four!). She reappears in Darksaber (flying her flag on the Knight Hammer), fights alongside the New Republic against Darth Caedus, and actually winds up as head of the Republic's successor for a while in Fate of the Jedi. It would have been really nice to see a character based on one or both of those two...