Certainly Sunak was a back stabbing tax avoider (perfectly legal though avoidance is), without even the brains to see that the tax issue would inevitably emerge and look terrible. Truss has political views that I personally dislike, plus a history of 90, or 180° turns in her views, so not likely to appeal much to sometime Labour voters who went for Boris for reasons around Brexit, levelling up, or personality (as far as I can see she has none).
I'm sorta with you on Starmer, though. Every time he says anything, you get the impression it has gone through multiple edits in his head before coming out of his mouth, so as to not alienate various bits of his party, or voter groups.
Consequently, it's never at all attention-grabbing, and again demonstrates no personality whatever. Thinking I might have to vote for 'none of the above' at the next election.