What I find really impressive about the above comparison is how everything of the left side looks like a twentieth century factory of some sort (in one or two cases perhaps a milking shed) and the other side looks futuristic. How the heck did you do that?
You know, once you stop counting pipes and tanks (which is like observing that a chimp and a human both have arms and legs) and just look from one side to the other, you would have to put on a welding mask and close your eyes to get the impression there is a comparable degree of apparent technological advancement. Or are you actually saying you don't see that? That to you, the left side appears just as "advanced" as the right?
The stuff on the right looks like a set, attempting to resemble the stuff on the left on a modest TV budget from the 1960's. Note the forced-perspecive pipes behind the grate, to give the illusion of scale and, well, more big pipes.
The only thing "advanced" is the bank of computer consoles, and STXI had touchscreen terminals dotted throughout their brewery.
Compared exclusively to TMP I could see your point. But TMP changed engineering from TOS as much as they changed the Klingons. It went a decentralized load of pipes and tanks, none of which had a set function (in fact, Engineering's location itself fluctuated between the rear of the saucer and the secondary hull!), to a chamber built around a glowing blue tube.
As I said in my earlier post, the engineering section in TOS was supposed to be much larger and more complex than what they could afford to depict in the 60's. Ben Finney certainly could not have remained hidden for days in the TOS engine room as we saw it!