Problem is that shared infrastructure shouldn't be operated for profit. But American conservatives seem to think that's the way to go. If infrastructure is shared, then there's every incentive for a business to sell even if the infrastructure can't handle it.

That being said, it's a required thing. This is why we have society in the first place. If every customer had to have their own cell infrastructure, it would be a mess and a waste. I mean you are sold unlimited bandwidth at let's say 1Gbps on 5G. There are about 1 cell tower node for every 1000 people in the US across the country. If we build enough infrastructure for everyone to use it at full speed each tower node would then need to be able to handle 1,000Gbps. That's just not possible with current technology. So should we build one tower node per person plus all of the cabling and routers to handle that much traffic? Does everyone really need to be able to download a gigabit of data every second of every day? What would you do with that data?

What internet infrastructure is designed for is peaks of up to that speed for short bursts. Not sustained speeds. And then sharing that infrastructure. Just like if everyone were to turn on their water at the same time, no one would get more than a drip, but does that ever actually happen in real usage?

The difference is that water infrastructure is owned collectively, so it is more equitably developed to make it available to all as equally as possible, rather than just to those who pay more for it.

At that point is where mine and your opinion diverge. In what sustainable business does one sell more of anything than they can maintain responsibility over?

What they're talking about is the mobile provider overselling service. Because they know that for the vast majority of the time, everyone isn't going to be demanding huge amounts of bandwidth all at the same time. Cable/GPON fiber ISPs do the same thing.