TOS was 1966-69. 2001 was made in '68. SW was made in '77 and ushered in the era of the "fun" blockbusters (With Jaw's help). TMP came out in '79. It missed its era by just a few years. One might argue if TMP had come out in the early to mid-70's, it might have been received and remembered completely differently.
It didn't do too badly. It's aesthetic isn't too out out of (don't forget, part of this criticism stems from it NOT being a Star Wars rip off. An odd criticism.) It's era. 2010 comes out a few years later, and there are plenty of 'clean' Sf films. As an aesthetic, TOS itself is very clean, even the engineers aren't shown covered in grime....because that's a bad idea in real space travel as well as pretend space travel in part designed to show off colour television.