Agreed Nick, These days the cars have SO much downforce that even an average car struggles against a very good one if it doesn't have the downforce.
Back in the 80's./90's they had little downforce and so it was all about chassis and mechanical grip....and driver talent. So there was more chance of a mid-bottom grid car to have good results....like the Minardi in the hands of Pier Luigi Martini, who had some awesome races with a bit of a shed....and the Leyton house car, under powered but had an awesome Adrian Newey designed chassis.
....Also the Lotus in the hands of Senna.
but that is what made that era so exciting as it was so close.