Seven of Nine was a awesome character who is as memorable as Spock.
It's hard to take the rest of your opinion seriously when you open with gems like this.
I see no demise of the Borg as a credible threat. New defenses & technologies came & made the Borg less of a threat, and Seven of Nine just assisted in that process of giving Starfleet a better understanding of the Borg that allowed Starfleet to faster develop new strategies, and technology to better fight the Borg.
The Borg were completely emasculated as a credible threat by the end of Voyager. They were a shadow of their former selves by the shows end. It's a good job that Voyager had other major villains to fall back upon - The Vidiians, the Kazon, Species 8472, the Hirogen - all so memorable. Oh, wait......
If the Borg were to remain static villians forever it would be boring before too long since it would be the same everytime, and that would become contrived very shortly since there would have never been any improvement on defense against them (oh looks its the Borg...Been there done that...wake me up once they finish assimilating us...ZZZZZZZZZ).
That would only ever have happened with over-exposure. The Borg were the most feared adversary on TNG, and they appeared in six episodes, each giving a different slant on the Borg species. Voyager, on the other hand, took them, used them, used them again and again, and again and again. To their credit, they tried to evolve them. To our disappointment, they failed. Spectacularly.
No I am saying that TNG isn't TOS. Voyager was the most similar to the TOS. Voyager was a return the the classic Trek formula. The producers ever said so:
This, and the quotes supplied - Of course what they intended to achieve, and what they actually did, don't always bear any relation to each other.
Voyager was perhaps SUPPOSED to be similar, thematically, to TOS, but in the end, due to its extremely poor execution, you can't really labour that point to much as it comes across as utterly ridiculous.
If Voyager's intent was to recapture the magic of TOS then this is evidence enough that you can't catch lighting in a bottle twice.