@shibao dark matter doesnt (haha) matter in all this , dark matter is an observed phenomenon , not something we "came up" with
as for the dark energy thing , its not "free energy", the Λ-CDM model axxounts for it (hence the Λ) and without it LOTS of shit break
i honestly dont know (yet) enough cosmology to underatand this paper so i cant say much more , but if u want something divulgative i can recommend this video by angela collier (honestly one of the only well behaved science xommunicators on youtube ) m.youtube.com/watch?v=PbmJkMhmrVI