I agree that 256 GB should have been standard. But for me 128 GB is plenty enough since I don't have anything locally that needs that much storage. Music and photo/video are online solutions with like cached copy of I really need it.
In terms of SD card, not sure when I last used SD card on a phone and I don't like SD cards. Prefer the faster onboard faster flash storage. That's why I also never hate Pixel or iPhone since never use SD card even if it's available
Obviously everyone's usage/preference is different and for me 128 GB is minimum storage I need before it becomes deal breaker. 256 GB is sweet spot.
Also, for the 512 GB option Samsung should have also increased RAM to 16 GB. Even then I would have probably just gone with base model this time around.