I think my reply was "misplaced" I cannot find it. Here it goes again
I can understand your concern. You were getting beautiful details with the 7MP and 16MP cameras, but now with 24MP you are not seeing more. You should consider that as the sensor resolution goes up, so must the lens's resolution. An indifferent kit lens which showed details at 7Mp may not be upto it with 24MP. The current kit 18-55 VR-II supplied with D3300 is way ahead of the original 18-55. It is sharper and has better micro contrast.
Coming back to your problem. You need better glass. If the sharpness and detail of a 7MP sensor are to be there in 24Mp sensor then
. The sharpness has to be doubled
. The micro contrast has to be doubled
. Distortion halved
In short the lense has to be ahead of the sensor and not behind it. There are many lens which are extremely sharp, have great micro contrast and in genera whose images just "Pop Up". Unfortunately most of then cost an arm and a leg. You want excellent details and micro contrast go get the Zeiss Otus 55mm. You will get all your $4,000/ worth. On the more affordable side you can try the Sigma Art series. Both their 35mm and 50mm are way better than the corresponding Nikon offerings, but even here you are talking of $600-1000 range.
If you want extremely low cost solution get the Nikon 50mm F1.8D. It is only $100, but at F5.6-F8 rivals many extremely expensive lens in IQ. I would suggest that you invest the hundred dollars to buy this lens.
. Set up you D3200 on a heavy stable tripod.
. Set the ISO to 100 or 200 (they have essentially same noise).
. Set the aperture to F8.
. Shoot your favorite scene. Use ND filter to increase the exposure time if needed.
. Now if you have an older camera, do the same sequence with it.
. Capture in RAW.
Now open up the RAW files in the software you use. I would suggest that you use View NX-2, as it will give the best colour and lense distortion works. Check the details and if you had the older camera compare the details.
If you are still not satisfied, then rent a Canon and perform the same sequence. Check the details. If you like the Canon details better, go for it, but I still cannot figure out how an 18MP sensor will have more detail than a 24MP sensor. Colours - may be, ISO noise - maybe, resolution - not at all.