There were people who hated the animated series and didn't want it to be part of "their" Trek.
Indeed! I once knew people who were angered by the humorous Arex and M'Ress cameo in Gerrold's "The Galactic Whirlpool".
And, as I once discussed with the late Janet Kagan, adding M'Ress to "Uhura's Song" might have given the search for the aliens' cure more interesting since they were also felinoids. She agreed, but hadn't much knowledge of TAS.
Of course, TAS fans remember the day when Arex and M'Ress were ordered to be written out of the DC Comic series, and (some of us) celebrated when they suddenly arrived in "Gateways: New Frontier: Cold Wars".