The vast majority of the people that commissioned them, including very successful series, wanted it done as fast as possible to get it to TV ASAP. Often they had toys lines up for Xmas that needed to be synced up with schedules. I know people that had worked on some very famous cartoons, including the 1980s Ninja Turtles, Care Bears, etc and the studios commissioning them were very willing to take errors, substandard, and otherwise less than ideal work to get it to market on time (much to the frustration of the artists who were being treated like factory line workers). They did say the creators of Ren and Stimpy were fantastic to work for and they had all sorts of fun Easter eggs added.
Anyways, it does not surprise me that a lot of the work from this era was not taken care of, especially some of the more forgettable episodes of popular shows. A lot of the early licensed work on Netflix was obviously copied from DVD/Blue Rays at the time, too. It can be a lot of work to properly deal with aspect ratios, colour correction, de-interlacing, as well as upscaling the very low analog resolutions.
Maybe AI can get good enough to fix it now, though.