I think it has got worse though, the IPPR replicate a 1944 poll where 35% of people thought politicians were 'out for themselves' and last time they did it, it was up at the high 60's % . Of course you have to take into account the wartime context and level of deference back then etc but I think the biggest collapse has been from the 2014 position to the end of 2022 with 2021/22 causing a lot of damage in particular.
The irony is in our polarised country it's one of the few things that brings people together - whether you're tory or labour, leave or remain, degree educated or not, working or middle class, the numbers are all in the 60%'s for mistrust of politicians.
Notwithstanding the chaos of the final 2-3 years of tory rule, and though I don't have hard evidence for it, I do think social media is making the problem significantly worse too. It's making our children ill and poisoning our public discourse but still we plough on.