I disagree as my normal use showed the difference in IQ quite clearly, but other than that yes, if your normal use is in good light and you only look at whole images on small screens then the differences may indeed be difficult to spot.
I think what's acceptable IQ wise is the key here. Tiny sensor compacts can disappoint and personally I've chosen 1" sensor cameras as the minimum I'll use for my uses and expect reasonable IQ.
My "normal" for holiday shots is mostly fine weather, and frequent use of zoom.
I took a TZ1 with me to the Philippines in 2008, a TZ10 in 2011, and then later a TZ60
Never been disappointed with the results, and even the occasional night shot and dull weather were fine, but I guess my expectation/equipment balance was known beforehand.
I at no time wished I had taken something better.
I agree I don't have a big screen, my biggest PC screen is 24", and my normal working screen is 17", and even with crops, it is fine on those.
I have no doubt there would be an improvement with the bigger sensor, but I wonder how quickly that advantage would be lost to the longer zoom of the TZ70 when it was needed.
That sony has a max focal length of 70mm (35mm eq) and for distant things, the TZ60 wouud give a better image than a full frame with a 70mm lens and then cropped.
So I still don't see a magical improvement