That’s not a conclusion that I would draw. Most hearing aids suppress noise just fine by beam forming to pick out the speech in front and block out sounds in the back and on the sides. The Oticon OPN/S/More don’t block out sounds like the rest but they do help suppress noise when speech is going on as well.
They just can’t do it like the way you want to see above (just universally occlude/block out everything then recreate it in a control fashion internally) due to the receiver’s limitation in reproducing low frequencies faithfully.
A person with normal low and mid frequency hearing usually can block out low and mid frequency noise using their brain hearing just fine, so they can wear open domes and not have an issue with noise. Mostly they wear hearing aids to help them hear high frequencies better, but they don’t really rely on hearing aids to block out the noise, they rely on their brain hearing to do that. The ability to hear the highs can help them make differentiation over various noises to help their brain tune out the noise and focus on what they want to hear better.
If you’re in this category, BUT your brain hearing can’t block out the noise, then wear more occluded domes or molds to help you block out the noise. The trade-off with this is that you no longer get to hear the low frequencies the way you’re used to anymore. It’s no big deal if you just care about speech. It’s a big deal if you want to listen to music with strong bass. But an easy workaround for this is to just slide your occluded domes or molds out a little bit to let the bass in when you want to listen to music.