The correct way to moderate is to be civil and treat "low quality" users as human beings. Reserve inhuman bans for inhuman users (bots).
As public online discourse becomes a more engrained part of normal society, shadowbans may even end up being an action that, in and of itself, end up being regulated and controlled. Shadowbans can help create a better and freer society for everybody, but they can also be used to create a dystopia. In some ways it's akin to a real world weapon. A firearm can be used to uphold and protected great values, but it can also be used to impose horrific ones.
Since when is getting a new phone number that receive SMS an insurmountable expensive? There are literally dozens, perhaps hundreds of services selling this. Example [1] https://www.textmagic.com/sms-pricing/ seems to cost me 7c per text received with no account fees, and I only need it to receive a sign up message.
That is far from "organized and funded". People paid $8 to make troll accounts on Twitter when it was possible.
You are correct that burning a SIM card is not that expensive.
However, your example of a text capable VOIP number is not a good one. FAANGs require a real mobile number and these texting services (twilio, for instance) will not work.
All of this to say:
It’s a bit more expensive than you think. If you really care about succeeding, you’re going to need to burn a SIM card.
The entire reason shadowbans exist and have existed for decades is because there's an inherently unsolvable problem with certain users that extremely fixate on certain users or communities. If you think they can be treated by being civil then I don't think you've been a moderator for any extensive period.