Not sure I'm following you as that wasn't the OP's original question. The way I learned it [basic electronics but I think it applies here too] is that the output can never be better than the input. A 480 [interlaced or progressive] input [by todays standards] is crap in and so it will be crap...
I think it is, especially with a quality display. 480i to 1080P was a bigger leap [optically] than 1080P to 4K. 1080P still looks awesome today even on my 135" screen, assuming good source material. True 4K gets into more pixels [resolution] than the human eye can decipher so an up converted...