On my very first watch of TNG, I was so annoyed the first couple of times I saw Lwaxana or Q dominate an episode, but by the end of the series I was cheering every time they showed up!
I didn’t know the story behind it until recently, but the first time I watched DS9, I thought “Wait, are they really trying to get away with replacing this awesome character with a younger, cuter actor?” I assumed it was a desperate bid for ratings.
I thought they both did a great job, but we’d had 6 seasons to get attached to Jadzia!