I agree with you on every point, for the most part.
It was not strong casting from the start. The characters all grew on me, and I like them all, but a lot of them couldn't act. Harry Kim, Tom Paris and Chakotay were the worst offenders there. I was actually glad once they focused more on Janeway, The Doctor, and 7 of 9, because they were the redeeming characters/actors of the show.
I found their villians of the week to generally be better than their recurring ones. The Kazon were the worst villians ever. I thought the Vidiians were actually a neat idea, but they didn't use them enough. The others were hit and miss. They did have some that I thought were cool though, like the Krenim, and the think tank.
And the ending of Endgame was such a cocktease. They got home in seven years, with so many accomplishments (including the feat of getting home itself), and we don't even get to see them reunite with their loved ones. At all. Overall I thought it was a fairly good episode though, but I agree with every criticism I've heard of it.
DS9 did it right. They wrapped up the main Dominion arc in the first half of the episode, then left the rest for every character to get their own conclusion. It was by far the most satisfying finale of the bunch imo.