Not true. In good light the X camera is looking great but the small sensor is the limiting factor so its low light capability is hampered.
For a "better" camera pretty much anything from a Sony RX100 with a 1" sensor through Olympus/Panasonic M4/3, through Fuji APS-C into Sony/Nikon/Canon Full Frame and beyond is going to be a "better" camera .... in varying circumstances but all come with a compromise of image quality vs weight/size/cost.
The true question is what is it that you are lacking today? what is it that you are looking for? What do you want to shoot?
With that then a recommendation can be made. Without it, we can only resort to the typical consultant response... "it depends..."
If you are looking for a better all round snapper then I would look at a 1" sensor camera like a RX100 or the Nikon 1 system. If you need more reach (zoom) then maybe something like one of Sony RX10 models MKiii is latest and is very good but not cheap. If you are not looking for a changing focal length, then the Fuji X100F. It is a cracker apparently. Owners of X100 series cameras love them.
If you want to get into interchangeable lens cameras (tread carefully, that is a deep dark money hole)... then you cannot go wrong in the Sony A6000/6300/6500 (note the kit lens on the 6000 is rubbish so not a good representation of what this is capable of - for an example of someone making magic on an A6000 series camera look at
@needfx 's images on here), Olympus E-M10,5,1, or Panasonic, or Fuji XT10, X-T2, X-Pro2
If you want Full Frame, at this stage, quite simply, don't go there. Notice I didnt say need, if this is your first camera then don't waste money on FF at this stage as you don't know what you need yet.
I think as someone loving the iPhone X, then I think you would be happy with an Olympus E-M5 or E-M10 kit of some sort to start with...
If you look round the Picture of the day threads on here you can see we all shoot with a vast array of differing equipment but we all produce great images.