The question, as other's have correctly noted, conflates two issues, the 974 generations before Adam, and the creation and destruction of worlds before this one. I've come across two sources that shed some light on both issues: one from Rabbi Aryeh Kaplan, and one from Alexander Poltorak, a Jewish theoretical physicist.
In Rabbi Kaplan's The Age of the Universe, he proposes that according to the Sefer HaTemunah, as it is interpreted in the Sefer Livnas HaSapir (according to Rabbi Kaplan, the "most authoritative interpretation"), we are in the 7th sh'mitah cycle of 1000 years. Under this interpretation, the world was 42,000 years old when Adam was created. Naturally there are many different interpretations of the Sefer HaTemunah, so this answer is only meant as an introduction of Rabbi Kaplan's article, in which he examines many such interpretations. However, Rabbi Yitzchok deMin Acco argues that the years in the Sefer HaTemunah are G-d's years, since they preceded man. This view Rabbi Kaplan combines with the Sefer HaSapira to argue that therefore the Sefer HaTemunah is speaking of 42,000*365,250 years, or about 15 billion years. Meaning the universe existed for 15 billion years before Adam, whatever the nature of these "years."
The second article I would point you towards is here. The premise is quite simple. Quantum Mechanics says the collapse of the wavefunction is caused by observation. Poltorak posits here that it's not the physical observation, per say, but consciousness deriving from the G-dly soul within man (and here he departs from other QM consciousness interpretations that theorize animal consciousness is enough to cause collapse). It's important to note that wave collapse by consciousness is just as valid an explanation empirically as any other interpretation of QM. Under this interpretation, until the first observer with a G-dly soul, Adam, the universe existed in a probabilistic superposition of all possible universes. Therefore, there were an infinite number of potential universes, one for each theoretically possible universe, that were "created [by G-d] and destroyed" when Adam's consciousness limited reality to just one single, tangible universe.
Putting the two together, one possible interpretation of the 974 generations before Adam is that they existed and didn't exist simultaneously. Being animal man, and lacking the Image of G-d and/or the Breath of G-d, they could play no role in the collapse of the universal wavefunction, and therefore where "stuck" in that immaterial state described by the probabilistic wavefunction. Not until Adam was there a conscious observer, and therefore, the age of Creation is counted from Adam, meaning the number of years since he collapsed the universal wavefunction. But since that collapse materialized ~13 billion years of history, the universe has two ages, each representing a different perspective. Naturally, the "truest" one is the number of years since Adam. Under this interpretation, the 974 generations of "wicked" men are the conscious-less homo-sapiens that "existed" before Adam, but were only materialized when Adam first observed the world.
This is not to say that any of this must be correct. That's a task for brighter and more scientifically and Kabbalistically educated minds than me. But seeing your question, and having come across these two Jewish sources from in my own searchings, it would be wrong not to share them.
I think there is a simple message behind both: appreciating our existence, in this perfect world, which is multiple times, "revisited", as it were.
– Binyomin Oct 17 '20 at 21:30