While that was definitely a huge problem with the plot device called the Nexus, the larger problem was its description: a place where your greatest wishes come true, and that it's so addictive that you'll never want to leave. Well, not only was it quite easy for Picard and Kirk to leave, but Kirk's greatest wish was obviously to command his ship again because he hated retirement. And yet the Nexus gave him the fantasy of...being retired?
I think the fantasies were more like reliving decisions and regrets to change the outcome, like living in lots of alternate universes all at once. Kirk is regretting leaving Antonia to go back to Starfleet...possibly just before the launch of the B even. If he hadn’t gone to that, he wouldn’t have got blown into the nexus, and maybe the crew of the B would have found another solution without Kirk telling them to get into transporter range etc. Picard is living the fantasy of a life with a family...and just like in dreams, all the memories that match that dream just slot into his head. The nexus is like a sort of permanent dream state for your consciousness, outside of time. Which explains a lot about things like the Guinan shadow, why Soran wants to get back in it, and even some of Guinans odd abilities and time sensitivity. Maybe when they dream, the Nexodused people link up with that part of themselves still living out all the permutations or reality in the nexus.
This is stuff that makes sense about the Nexus.
Using it to move your physical body in time and space?
Not so much. Only in a locality where the Nexus has actually been (to within its range, it sweeps the mountain to get Soran and Picard after all...yet as far as we can tell, not the rest of the crew or indeed Guinan, because that would have been an interesting and longer film...all the crew choosing to leave their fantasies and go back, behind Picard and Kirk, maybe even a redeemed and now whole Soran.) seems to make sense, but that’s never explained in the film, it needs a tweak of Nexus Guinans dialogue with Picard.
I think they thought some of this through, but forgot to actually get it into the dialogue, either explicitly or implicitly (which they did mostly manage with the nature of life inside the Nexus at least. And with its name.)