I reckon you're spot on with this take. I agree we've been infiltrated by malign forces over time, some of it NGO funded, and I do wonder if it's because there is little or no redress when perpetrators do get caught.
One thing I do believe has happened and having lived through it think this graph illustrates it perfectly, the distribution of the right and left (here shown by the dems and the republicans in the USA)
if it isn't showing, just google "The Economist Asunder" and it will show under images.
I think the graph illustrates the UK too. I agree with 1994 in the wake of Thatcher and Reagan, I agree with 2004 moving to the left a point after years of Clinton and Blair, and I also agree with 2017 when even parties traditionally right governed left, Corbyn with 40% in a GE. I don't think we are too far from the 2017 position today.
People talk about polarisation and division in politics all the time, to reduce this we need a big overlap like in 1994 and 2004, shared values. This has been very diminished by 2017.
So what has caused this division. Well the BBC and MSM will blame it all on the mythical far-right, but as we can see from the above while the traditional republican (or UK Conservative) has moved a little to the right....from 5 or 6 to 6.5 average, the real change is the democrats or left moving from 4 or 5 to 2. If these people has stayed where they were in 1994 or 2004 there would be far less division now.
So 30+ years ago someone as far left as Starmer would be viewed as having limited appeal, however with the profound shift of the left we can see why he was elected.
If I had to mark the current UK parties I'd be somewhere around.
SNP/ Plaid/ Greens - 1.5
Labour - 2
Lib Dems - 2.5
Conservatives - 4.5 (not fooled by what they say, I saw what they did)
Reform - 6.5