Impeachment occurs within the framework of the Constitution. In that sense it's a legal process.
and no where does it say it has to be fair. It should be fair, but it isn’t. If the voters don’t like it, they can vote their reps out next November.
The same applies in all legal processes. Doesn't make those processes not legal.
Did the SC interfere in the Senate rule that a bill needs 60 votes to pass. No. I could go on but the principle should be clear. Did the Supreme Court interfere with the House rule that during committee hearings, each Rep gets 5 minutes of questioning? No. What if a Rep gets upset because they want 10 mins per questioning period. Do they sue and take it to the Supreme Court
Has the Supreme Court interfered as to how many Reps or Senators are seated in a committee? No and that is one the most contentious and partisan issues every two years. How many committee members and the mix is fought tooth and nail by both parties. I could go on and on and on.
Impeachment rules are no different and the SC shouldn't and won't intervene. Each branch is co equal and the SC can't dictate to the House its own impeachment rules.
It's political and the SC knows if the voters don't like how the House is run, they can be voted out which is the appropriate remedy.