I think they could be successful in doing a mix, like r rated TSS existing in the same universe as Wonder Woman etc - they just need to make sure the films are consistently decent*. The MCU has films that are better than others, but none of their films have been as egregious to the general public as BvS, JL, WW84, or Suicide Squad. Again, I think the DCEU's longevity will be determined by the Flash movie, and maybe Black Adam too. It remains to be seen whether the public will accept one and done "elseworld" type movies effectively outside of the batman brand. I suppose we'll see once the Abrams/Coates Superman film is released. I guess it could be a result of the Flash movie's multiversal plotline, in which case it may help audiences understand more?
*Of course R rated connected universe movies may not make as much as other, more family friendly offerings, but as long as there's a profit it's all good.*