Repeating here what I have raised elsewhere: I find the timing of this decision unfortunate in that we have just upgraded Gerrit from a three year old version to a bleeding edge one, which brought major improvements such as hiding machine noise from code review discussions, or the ability of CI tools to leave inline comments. Satisfaction surveys based on people's experience with the old Gerrit version (which has been end-of-lifed a year ago, and which was mostly created before Google started stuffing UX desingers into the Gerrit team) are not necessarily indicative of how user-friendly Gerrit is now.
Topic on Talk:Wikimedia Release Engineering Team/GitLab
To be fair, none of the comments in the survey were about the things you mentioned (eg: inline comments or hiding machine noise) and more about generalized things like the workflow and the interface (which really hasn't change drastically). To put it in a different way: I don't believe anyone who choose to not use Gerrit will now move back to Gerrit due to this upgrade.
But point taken re timing.