The Gerrit UI is just bad (confusing). I don't like the "dated" criticism for work tools because whether it works well is mostly independent of it being fashionable - cf. Steve Jobs quote "Design is how it works". Gerrit's UI is both dated and confusing, but confusing is the major thing here. For example, "+1" and "-1" meaning "I like / don't like it" and "+2" / "-2" meaning "I approve / block it". The numbers are not summed up, the names are misleading. Or the workflow of writing a comment and then publishing it. Probably makes sense when making several comments (on different blocks of code), but it's too easy to forget the publishing, especially when writing a top-level comment where there isn't anything else to publish together.
Another thing I don't like about Gerrit is that they seem to play Tetris with UI elements, i.e. "wherever there's room to put it is where we put it". It's not as bad as it used to be and improving, and it looks less dated than it used to, too. There are also newish features like patch editing in the web interface.
All that said, patch queues / stacks and the rebase based workflow are nice.
Definitely, "feels dated" is very subjective. The other problem ("I feel like I'm fighting with the tool", "I'm jumping all over the place to do what I want") may be related to your "UI tetris" point, and I may be unnecessarily tying it to the UI feeling "dated".
ISTM that what is needed is to observe how people interact with the tool and then try to figure out how the workflow can be improved based on those observations. Or maybe I'm trying to interact with gerrit in some strange way - that's also possible.
The +1 / +2 for different labels aren't that confusing to me - additionally, in Chromium I found that gerrit is very descriptive when you on-mouse-over the buttons, but IDK if it's specific to this deployment or if that aspect got improved.
Another thing I don't like about Gerrit is that they seem to play Tetris with UI elements, i.e. "wherever there's room to put it is where we put it". It's not as bad as it used to be and improving, and it looks less dated than it used to, too. There are also newish features like patch editing in the web interface.
All that said, patch queues / stacks and the rebase based workflow are nice.