This, pretty much. It all depends on what you actually want to do with your camera; what sort of pictures do you take, and in what way can another cam actually improve things?
I had a D3300, as a small, light 'travel' camera. It did an excellent job, and produced some decent pictures. I mostly used it with the 16-85mm zoom, which was pretty good. The combo was a lot smaller and lighter than my D600 + 24-120 lens. The D3300 was small enough to carry around all day, yet still more than capable for most situations. I was actually surprised it was so good tbh; I'd considered a micro 4/3rds camera, but the larger sensor in the D3300 is just that bit better really.
So why did I let it go? Well; I do a lot of my photography in low light, and the D3300 does struggle a bit there. Images are 'noisier' at higher ISOs, than on my D600, which has a larger sensor. Overall image quality is slightly better on the D600 all round really. The viewfinder, which whilst good, isn't up to that of larger cameras (this is due to the use of a
'pentamirror' rather than a pentaprism found on larger cameras. So it wasn't as bright and clear, especially in low light. Nikon then introduced the new Z camera system; smaller and lighter bodies (mirrorless designs), excellent sensors, excellent lowlight capability, improved AF, etc. Still slightly bigger than the D3300, but not by much, and the camera with 24-70mm lens combo is still relatively nice and small and light. But I spent over £2000 on that. Which is a LOT of money. Which is something that, if you really do want/need a new camera, you'll have to accept. It will cost you. Loads.
A 'better' camera will offer certain advantages, but if you move up to full frame, will also come with extra size and weight. Even moving to a D7xxx camera will be adding size and weight. Although that will allow you to use existing lenses the same, plus offer the option of older AF-D lenses, which have a mechanical AF system. This will open up more photographic opportunities though, and the older lenses are often a lot cheaper than the current equivalents; for eg a 60mm micro (close up/macro) AF-D lens would cost around £150 or so,
second hand, yet a newer 'G' version, £100 more, for little real world benefit (faster AF maybe, but manual focussing is better for most close up stuff).
If you feel you have reached the limits of the capabilities of your current camera, then maybe it's time to 'step up'. If you feel the AF system isn't fast enough for the type of subjects you shoot, or the low light performance is a bit lacking, then yes, 'upgrade'. The D7xxx series are the way forwards; the D5xxx series are no better in terms of actual photographic capabilities than what you have, they just add things like a flip screen, wi-fi etc. Which you might not want or need anyway. If you want to keep it small, then the new
Z50 will offer lots of
performance benefits, but is a totally new system and you'd need an adapter (FTZ) to use your old/other F-mount lenses. Obviously it's best to go into a shop and try out the different cameras for 'feel', but not possible for at least a while yet. Still; you've probably got a bit more spare time to read reviews, watch videos etc atm.
The most important question you really need to ask yourself though, is the one regarding
Want vs.
Need. Only you can answer that.
