I don't think this is automatically the problem, Lucas wrote the original film as a stand alone piece, it had potential for threads of the story to be expanded but he didn't have a totally clear plan.
The difference here though is that I think the original film was designed very much as that, a stand alone piece, it setup the wider universe but gave a pretty free hand to its sequels in terms of building there own plot. The Force Awakens on the other hand is vastly different to that, its a film that I think it does a much worse job selling its overall setting and instead focuses on introducing a collection of mysterys. Its basically a film that tied down its sequel to trying to answer the questions it posed yet I think now its pretty clear Abrams never had answers to those questions planned out. People warned that this was Lost mk2 and I think that's very much come to pass, Abrams using cheap mystery's he has no answer to instead of actually writing good drama/characters.
As I feared as well this film was also very much tied down to the tone Abrams established in TFA which really doesn't suit Starwars at all for me, its like a very vague nostalgia memory of the series filtered though the blandest of modern clichés.(with none of the inspired wit of stuff like Guardians of the Galaxy or Thor Ragnarok). Given that these films are feeding on anti prequel feeling I think its ironic that actually there much close to the prequels in tone with there endless "roger roger"ing droids and the like. A lot of people actually ragged on Rogue One last year for being too serious but that film is much closer to the originals in tone.
Not that Johnson shouldn't take some of the blame for this but for me this film demonstrates what a massive mistake(at least artistically although I suspect it will feed into declining returns) Disney made firing Arndt for needing time to plan a scipt and instead hiring Abrams to rush something out quickly. The reality is great work takes long term planning from talent people, Lucas and other writers took years on the originals, Peter Jackson took years adpating Lord of the Rings, etc