It seems to me there's some deep revisionism going on with your PoV.
In 2017, Labour came within thousands of votes of becoming the governing party. Why, because Corbyn's policies were allowed to go directly to the people as the MSM didn't take him seriously.
I can't recall Corbyn being falsely accused of antisemitism back then, which became one of the weapons used in the MSM in the next election run.
I'm pretty sure you remember the MSM differences in presentation of Corbyn in favour of the utterly oafish Johnson!!
So, yes, you're wrong about people not reading manifestos. You saw what I saw in 2017. So, when the MSM presented utter lies over Corbyn in the next election attempt, what do you think the result would have been if they were forced to retract the lies, publically?
Do you not think peoples views would have changed?