Do you think this would've done better if Spielberg was/Disney wasn't involved?

I seriously doubt it.

Spielberg was very involved with Crystal Skull and 95% of the fan base hated that movie. That fact alone assured that Dial of Destiny wouldn't do as well as hoped.

If Disney is to blame for a financial failure, it's only because they invested too much money in a movie younger people weren't interested in. In the (well attended, but not sold out) theater I saw Dial of Destiny in on opening weekend, it was obvious that everyone there was old enough to have seen the first 3 movies in the theater as well.

Unfortunately no. The filmwork and composition were fine. Where it failed was having an Indiana Jones in an adventure story where he's not really doing anything. His primary function was the water transition. The rest of the story tried to have what's her name be the adventures. It's the same issue with mutt in the last movie. It would have been better had they made an animated Indiana Jones movie.

Id hazard a guess that most (casual) audiences thought Spielberg directed it anyway lol (abit like all the Jurassic sequels, some of which were just as big/bigger than the ones he directed)

Ultimately I think it needed a more known/iconic McGuffin to get audiences excited, especially for the final film/payoff, something big like Atlantis, Excalibur, or some big Christian artefact (body of Jesus or something) , also Short Round as the sidekick, with maybe some popular actress like Ana De Armes, Felicity Jones or Haylee Atwell as the (non romantic) female lead. Obviously keep the Nazis, Mads as the villain, and the WW2 intro with deaged Ford

Well, at least Indy won't be knocked out by a woman.