I'm fairly new to stacking so others might be able to offer better advice, but maybe it's that you're separating things excessively into separate PRs?
One mental model that helps me make sense of stacks is that the Graphite UI lets you merge stacks partially, from the bottom. This means that once the say bottom 2 out of 8 PRs are fully finished, you can merge them into trunk. Probably doesn't work always, but can be a good rule of thumb to make the PRs atomic in the sense that if you merge the bottom N PRs of a given stack, trunk will be fully stable.
From what you're writing it seems that the reviewers are trying to look at multiple PRs at once to be able to review the feature in full.
If you can separate the feature into independent bits (that all can individually land in trunk without stuff added in upstack PRs), then that's a good use of PRs. If you can't, then maybe it's better to make a bigger PR.
One issue Graphite tries to solve, that I'm too painfully familiar with, is wall-of-text PRs that are just hard to review or even hard to find time to review, that then end up blocking your devs. If your reviewers preferred how things worked before Graphite, then I think you should simply put more stuff into PRs to make them more "whole feature".