Lobbying IS illegal, outside the channels of private donation and sponsored solicitation.
https://constitution.congress.gov/browse/essay/amdt1-7-13-5/ALDE_00013494/
That's patently untrue, and why the distinction matters between what we have, which is lobbying where corporate entities can create a quid-pro-quo situation rather easily, and what any reasonable person would support: people telling their represtitives their interests and how best to represent them.
Sending a letter is lobbying. A phone call or email is lobbying.
You're not upset that lobbying is legal, you're upset that people with the ability to offer things more valuable than their personal vote as an individual aren't stopped from doing it.
So again, how do you envision people asking for things from their represtitives that isn't just "properly regulated lobbying" rephrased?