For what I saw yesterday they were identical: spring rates, slow bump, fast bump, anti-roll bar, caster, steering degrees, wings. Like everything or almost everything

I never saw this in real life or in any other sim, to be honest. I'd imagine that balancing the performance of the cars is different from literally giving the same setup to all of them, because, you know, what works for the C7R could not (and perhaps
should not) work for the Porsche. To me this seems to go completely opposite from how it should be.
I'd also assume that any sort of BoP should be done either in 'power output' (as in giving it a bigger fuel restrictor or less turbo pressure) or some aero changes like a faster car riding higher which would result in the rear diffuser being less effective, for example - and that suspension adjustments would be made to optimize grip and weight transfer for each specific car BEFORE all the BoP.
I just can't see the cars being balanced with literally the same setup. This, to me, is why they felt so weird - and quite slow too. My lap times are not far from RL GT3, for example, being somewhat consistent: 1:58:5 on Silverstone with the AMG, C7R, and Bentley, all with a few setup changes made by me. But with the GTE's I'm not able to go down more than 2:02 for some reason, no matter the setup changes I try. They feel a bit less powerful than they should be, and too oversteery even if I try my best to make them understeer.
The RL cars did ~1:57:5 last year IIRC.