Recently, I've decided to make it a personal task to watch through ALL of Star Trek. I grew up on TNG and watched it whenever I could. I mention this because I have a distant recollection of many of the stories I loved from TNG, but now that I'm more thoroughly watching through the original series, I'm starting to have personally "haunting" questions that make me curious about the Star Trek universe and why certain events played out the way that they did.
I've noticed that in TOS throughout at least the first season alien races tend to fall into two classifications-- humanoid races that, in regards to intelligence and strength, are much on-par with humans. This includes Vulcans, Romulans & Klingons and a few other incidental races that come and go as needed for a particular story.
There is also a second set of alien races that are not slightly but are rather significantly evolved beyond humans. These races tend to appear in one episode, do their "unbelievable" acts and conclude the episode assuming we never hear from them again, often for the sake and safety of humanity. These races include the people of Talos IV that could manipulate the perceptions of minds, the beings from "The Squire of Gothos" that could control entire planets and the Organians which were excessively peaceable people that were capable of seizing up all weaponry aboard all Klingon and starfleet vessels in the vicinity of their system.
Much of my knowledge of the Star Trek universe comes from my childhood watching of TNG. In TNG we saw multiple interactions of the Enterprise crew with Q and his race. The Q was, to my knowledge, the only major race encountered that was significantly more advanced that humans. This is quite a juxtaposition to season #1 of TOS, where in every few episodes we see a new race that has unbelievable powers capable of doing nearly anything imaginable.
It is my understanding that the Q stayed out of the galactic war with the Borg because they believed in letting the rest of the universe play out at its own pace, in its own way. This is why they never wiped out the Borg or provided limited protection for the United Federation of Planets.
However, as outlined above, in TOS many exceptionally intelligent and capable races existed that could take control of people, manipulate space/time or simply do whatever they wanted to do.
Where were these races in the war against the Borg? Were any of them ever contacted by starfleet and asked for assistance? Were any of them assimilated? Were they just out of site and out of mind as if they weren't part of the galaxy?
In my opinion, from the perspective of TOS there were NUMEROUS races that seemed capable of stopping or potentially destroying the Borg. Where were they during the time of The Next Generation and its subsequent movies?
I'm not really asking for a speculative answer, however, I am curious if this was ever addressed in any post-TOS material whether on the television show, in comic books or novels.