The work had to pass the quality test to make viewers care. Lou Scheimer was determined to respect the content, and that went a long way in making TAS work.
If a low-balling company like Hanna-Barbera produced TAS, fans would have revolted with episode one, as it is a bit distracting to see characters' arms slip off of the body, insignias switch colors, and backgrounds painted on the level of a pre-schooler with watercolors.
That was H-B in the early 70s, and as the other big U.S. animation house (on TV), ST was more than blessed to have Filmation handle the series, which--as seen right out of the gates in 1973--was the right direction.
But to your point:
What is wrong with respecting original work and the artists responsible for creating said work?
Are some fans totally incapable of enjoying anything not fed through the grinder of CG revision?
While on the subject of ST, TOS Remastered was a terrible experiement, since the space shots and the Enterprise look no more realistic than a video game sequence. How does that help tell the stories, or make them enjoyable?