I have had a read through that study, and I would consider the following points striking:

1. it is entirely US-centric. Extrapolation to the entire world from this study would be pretty fruitless — in the extreme example, Switzerland is a democracy that uses referenda more than most (any?) other country, and so any policy decided by one of these by necessity follows the will of the voters (though not necessarily their interests, of course).
2. it is focussed on a very specific period of time — between 1981 and 2002. What’s striking about that period is Reagan - Bush - Clinton - Bush – in general a rightward swing (3/4 republican, and Clinton was a ‘third way’ Democrat). Is it particularly surprising that these governments aligned with elite interests?

To give a counter example to this study: consider the exit to the gilded age. We have a period comparable to now, where political power was bought and sold; corruption reigned. However, the government of Teddy Roosevelt made a number of moves counter to corporate interests, breaking up monopolies, reserving vast swathes of national parks, legislation protecting food and drug adulteration (note: not an unequivocal fan of TR — I am not in favour of his gunboat diplomacy).

A more recent example: under the Biden administration, there was a significant uplift in antitrust efforts. Lina Khan was appointed to the FTC, and who knows what she could have accomplished given more time. In a UK-based example, we are (finally, thank fucking god) renationalising our public services. It is absurd to think this would have happened under the opposition.

TLDR: democratic socialism is possible; your study is a snapshot of conservative administrations in America and — no shit — they aligned with corporate interests.