The current UK offering is supposed ot have been restored under the approval of Nic Roeg.
Not to do the gentleman a disservice, I can only assume they modified the 'approved' version after he left the building.
It's not a grain problem - real film has grain and as you say remove the grain, you remove the clarity.
The problem is that there is only what can be descried as machine noise that is occasionally very heavy . It smears and makes some panoramic shots look very washed out, soft and lacking depth and overall very un-film like.
I
View attachment 153466 n the screencap here (borrowed from the other place) look at the upper right quarter of the picture - not only soft and smeary, but it looks for all the world lke a painted backdrop.
View attachment 153469
Look at the second one and you can see an odd effect in the faces of both Christie and Sutherland.
There are lots of other instances where it just doesn't look right. It would seem they have probaby tried to make the film look more modern, but have removed much of the definition in places.
As regards the Criterion version, I am told they have tinkered with the colour timing.
edited for afterthoughts