First things first, the poll you linked to only shows how popular Sunak is amongst voters who voted for Boris in 2019, rather than the actual wider UK electorate (although I'm certainly not arguing he's polling well generally). Therefore, it's worth baring in mind that the position of the Reform Party is currently very different to in 2019 when they didn't contest conservative seats, and the polling firm in the article even say that it's Reform that are causing the cratering in numbers. This begs the question that if Sunak moved more to the right, sure maybe he'd get more of these voters that he's recently lost, but generally shifting even further away from the centre is at odds with success in General Elections so it's a bit of a "damned if you do, damned if you don't" situation where the main problem isn't necessarily the PM in question, voters are just generally sick of the Conservatives, even if they're not big fans of Labour.
I think you're being overly generous with how easily the ideology and views of the four PMs prior to Sunak can be defined and summarised, beyond mere political spin. If you look at it through the lens of policy implementation and outcomes, it's pretty hard to define people like May/Boris/Truss/even Cameron to an extent.
Truss spoke about growth and the supply side, then tried to force through irresponsible demand side policies that were never likely to stimulate growth. What was Boris' policy agenda? His tenure was sort of dominated by COVID which makes it tricky to define, but one could point to things like levelling up etc. And while this goal is certainly admirable, there's very little evidence he put meaningful policies in place to achieve this. With May, like with Boris and COVID, her premiership was largely distracted by Brexit deal negotiations and a failed election campaign which prevented significant changes to policymaking elsewhere.
I think it's probably clearer with Cameron and this is partly because he was the longest serving recent conservative PM by a distance. I think most would generally put him under the banner of being a classic neoliberal. There were some progressive policies under him (e.g. same-sex marriage legislation). But again, it's difficult to distinguish his actual ideology from its context which was massive austerity after the GFC and a coalition government for 5/6 years, which is likely to have prevented him from doing quite a lot of what both he and Osborne would have ideally wanted to enact.
Given the UK has generally moved from shock to shock over the past 15yrs (GFC, Brexit, pandemic, energy/cost-of-living), I think it's slightly unfair to not view Sunak under the same contextual lens - i.e. being massively constrained by inheriting a weak political and economic position. I think a fairer view would be that most recent conservative PMs (possibly excluding May who was slightly more principled) have just been populists, thus lurch from one political/economic position to another without any real underlying ideological underpinning, and thus far Sunak has been no different.